Optical Device for Determining Pulse Rate

ABSTRACT

Some embodiments provide a wearable monitoring device including a motion sensor and a photo (PPG) sensor. The PPG sensor includes (i) a periodic light source, (ii) a photo detector, and (iii) circuitry determining a user&#39;s heart rate from an output of the photo detector. Some embodiments provide methods for operating a heart rate monitor of a wearable monitoring device to measure one or more characteristics of a heartbeat waveform. Some embodiments provide methods for operating the wearable monitoring device in a low power state when the device determines that the device is not worn by a user.

BACKGROUND

Recent consumer interest in personal health has led to a variety ofpersonal health monitoring devices being offered on the market. Suchdevices, until recently, tended to be complicated to use and weretypically designed for use with one activity, e.g., bicycle tripcomputers.

Recent advances in sensor, electronics, and power source miniaturizationhave allowed the size of personal health monitoring devices, alsoreferred to herein as “biometric tracking” or “biometric monitoring”devices, to be offered in extremely small sizes that were previouslyimpractical. For example, the Fitbit Ultra is a biometric monitoringdevice that is approximately 2″ long, 0.75″ wide, and 0.5″ deep; it hasa pixelated display, battery, sensors, wireless communicationscapability, power source, and interface button, as well as an integratedclip for attaching the device to a pocket or other portion of clothing,packaged within this small volume.

The disclosure provides methods and devices for activating, in energyefficient ways, HR monitor based on user motion and skin proximity. Thedisclosure also provides methods for operating the LED and photodetector of heart rate monitors to obtain accurate reading of heart ratetailored for different user characteristics such as skin colors.

SUMMARY

Details of one or more implementations of the subject matter describedin this specification are set forth in the accompanying drawings and thedescription below. Other features, aspects, and advantages will becomeapparent from the description, the drawings, and the claims. Note thatthe relative dimensions of the following figures may not be drawn toscale unless specifically indicated as being scaled drawings.

Wearable fitness monitoring devices having heart rate monitoringfunctions and methods for operating the devices are provided in thedisclosure.

Some embodiments of the disclosure provide a method of operating a heartrate monitor of a wearable fitness monitoring device having a pluralityof sensors including the heart rate monitor. The method involves: (a)operating the heart rate monitor in a first mode while also operating ina second mode configured to detect near proximity of the wearablefitness monitoring device to a user's skin, wherein the first mode isconfigured to determine one or more characteristics of a user'sheartbeat waveform when the wearable fitness monitoring device is innear proximity to the user; (b) from information collected in the secondmode, determining that the heart rate monitor is not proximate to theuser's skin; and (c) in response to determining that the heart ratemonitor is not proximate to the user's skin, ending operating the heartrate monitor in the first mode. In some embodiments, the heart ratemonitor is an optical heart rate monitor. In some embodiments, the heartrate monitor includes a photoplethysmographic sensor. In someembodiments, the one or more characteristics of the user's heartbeatwaveform include the user's heart rate.

In some embodiments, operation (a) above involves periodically operatingthe heart rate monitor in the second mode while continuously operatingthe heart rate monitor in the first mode. In some embodiments, operation(a) involves operating the heart rate monitor in the second mode occursno more than about 50% of the time.

In some embodiments, operating the heart rate monitor in the second modeinvolves pulsing a light source in the heart rate monitor at a secondmode frequency and detecting light from the light source at the secondmode frequency; and operating the heart rate monitor in the first modeinvolves pulsing the light source in the heart rate monitor at a firstmode frequency and detecting light from the light source at the firstmode frequency. In some embodiments, the second mode frequency isgreater than the first mode frequency.

In some embodiments, operating the heart rate monitor in the second modeinvolves pulsing a light source in the heart monitor at a secondfrequency; detecting light from the light source at the secondfrequency; and determining whether the light detected at the secondfrequency has an intensity and/or pattern indicating that the light fromthe light source has interacted with the user's skin. In someembodiments, the pulsing the light in the second mode source involvesemitting a succession of light pulses, some having variable intensityand others having constant intensity.

In some embodiments, operating the heart rate monitor in the second modeinvolves: emitting a succession of light pulses of variable intensity;and determining whether detected light corresponding to the successionof light pulses has a variable response corresponding to the variableintensity of the light pulses.

In some embodiments, the disclosed method for operating the heart ratemonitor further involves operating the heart rate monitor in a skincharacterization mode configured to determine at least one setting foroperating the heart rate monitor in the first mode. The operation in theskin characterization mode involves: (i) pulsing a light source in theheart monitor by emitting a succession of light pulses of variableintensity; (ii) detecting an intensity, a variation in intensity, and/ora pattern in intensity of light after the pulsed light has interactedwith the user's skin; and (iii) determining a response characteristic ofthe user's skin from the intensity, variation in intensity, and/orpattern of intensity detected in (ii). In some embodiments, the methodfurther involves using the response characteristic of the user's skin toadjust the heart rate monitor's gain and/or light emission intensity foroperating in the first mode. In some embodiments, the responsecharacteristic is dependent on the opacity of the user's skin. In someembodiments, the emitted succession of light pulses of variableintensity from (i) is used in the second mode as well as the skincharacterization mode. In some embodiments, operating the heart ratemonitor in the skin characterization mode involves periodicallyoperating the heart rate monitor in the skin characterization mode whilecontinuously operating the heart rate monitor in the first mode.

In some embodiments, the plurality of sensors of the device includes amotion detecting sensor. In some embodiments, the motion detectingsensor includes an accelerometer, a magnetometer, an altimeter, a GPSdetector, or a combination of any of these. In some embodiments, thedisclosed method for operating the heart rate monitor involvesdetermining from information output by the motion detecting sensor thatthe wearable fitness monitoring device has had been still for at least adefined period; and in response to detecting that the wearable fitnessmonitoring device has had been still for at least the defined period,performing operation (c) described above.

In some embodiments, the method for operating the heart rate monitorfurther involves, prior to (a) while the first mode is not operating:(i) detecting motion of the wearable fitness monitoring device using amotion detecting sensor and/or detecting proximity of the heart ratemonitor to the user' skin by operating the heart rate monitor in a thirdmode; and (ii) initiating operation of the first mode of the heart ratemonitor when the wearable fitness monitoring device is determined to bein near proximity to the user.

The embodiments described above relate to detecting the device in anunworn state, while the ensuing embodiments relate to detecting thedevice in a worn state.

Some embodiments provide a method of operating a heart rate monitor of awearable fitness monitoring device having a plurality of sensorsincluding the heart rate monitor and a motion detecting sensor. Themethod involves: (a) detecting motion of the wearable fitness monitoringdevice using the motion detecting sensor; (b) in response to detectingthe motion in (a), operating the heart rate monitor in a worn detectionmode configured to detect near proximity of the wearable fitnessmonitoring device to a user's skin; and (c) upon determining via theworn detection mode that the wearable fitness monitoring device isproximate to the user's skin, operating the heart rate monitor in afirst mode configured to determine one or more characteristics of theuser's heartbeat waveform. In some embodiments, the worn detection modeoccurs no more than about 50% of the time. In some embodiments, (a) isperformed when the heart rate monitor is not operating or is operatingin a low power mode. In some embodiments, operation (a) involvesdetecting an output from the motion detecting sensor, wherein the outputexceeds a defined threshold.

In some embodiments, the method further including prior to (a): (i)operating the heart rate monitor in the first mode while also operatingin a second mode configured to detect near proximity of the wearablefitness monitoring device to a user's skin; (ii) from informationcollected in the second mode, determining that the heart rate monitor isnot proximate to the user's skin; and (iii) in response to determiningthat the heart rate monitor is not proximate to the user's skin, endingoperating the heart rate monitor in the first mode.

In some embodiments, operating the heart rate monitor in the worndetection mode involves pulsing a light source in the heart rate monitorat a worn detection mode frequency and detecting light from the lightsource at the worn detection mode frequency. In some embodiments,operating the heart rate monitor in the first mode involves pulsing thelight source in the heart rate monitor at a first mode frequency anddetecting light from the light source at the first mode frequency. Insome embodiments, the worn detection mode frequency is greater than thefirst mode frequency.

In some embodiments, operating the heart rate monitor in the worndetection mode involves: emitting light pulses from a light source inthe heart rate monitor having a second frequency and/or phase; detectinglight from the light source at the second frequency and/or phase; anddetermining whether the light detected at the second frequency and/orphase has an intensity and/or pattern indicating that the light from thelight source has interacted with the user's skin. In some embodiments,emitting light pulses from the light source involves emitting asuccession of light pulses having variable intensity. In someembodiments, a first one of the succession of light pulses has anintensity at least 5 times greater than a second one of the successionof light pulses. In some embodiments, the succession of light pulsesincludes a first set of pulses having an intensity providing variableresponse when interacting with light skin, and the succession of lightpulses also includes a second set of pulses having an intensityproviding a variable response when interacting with dark skin. In someembodiments, operating the heart rate monitor in the worn detection modeinvolves: emitting a succession of light pulses of variable intensity;and determining whether detected light corresponding to the successionof light pulses has a variable response corresponding to the variableintensity of the light pulses.

In some embodiments, the method of operating a heart rate monitor of awearable fitness monitoring device further involves: determining frominformation output by the motion detecting sensor that the wearablefitness monitoring device has been still for at least a defined period;and in response to detecting that the wearable fitness monitoring devicehas been still for at least the defined period, powering down thedevice.

Some embodiments of the disclosure provide methods for determining skincharacteristics of the user wearing a fitness monitoring device. Someembodiments provide methods for adjusting the operation of a heart ratemonitor of the fitness monitoring device. Some embodiments provide amethod of operating a heart rate monitor of a wearable fitnessmonitoring device to adjust at least one setting for operating the heartrate monitor. Operation of the heart rate monitor involves: (a) pulsinga light source in the heart monitor in a skin characterization mode byemitting a succession of light pulses, at least some having variableintensity with respect to one another; (b) detecting a variation inintensity of light from the light pulses emitted in the skincharacterization mode after the light has interacted with the user'sskin; (c) determining a response characteristic of the user's skin fromthe variation in intensity of light detected in (b); and (d) using theresponse characteristic of the user's skin to adjust a gain and/or lightemission intensity of the heart rate monitor operating in a first modefor detecting one or more characteristics of the user's heartbeatwaveform.

In some embodiments of the method, the response characteristic isdependent on an opacity of the user's skin. In some embodiments,operating in the first mode and operating in the skin characterizationmode are performed concurrently. In some embodiments, operating in thefirst mode and operating in the skin characterization mode concurrentlyinvolves periodically determining a response characteristic of theuser's skin while continuously operating in the first mode. In someembodiments, the skin characterization mode occurs no more than about50% of the time.

In some embodiments, operating in the first mode involves pulsing thelight source in the heart rate monitor at a first frequency anddetecting light from the light source, after the light has interactedwith the user's skin, at the first frequency. In some embodiments,operating in the skin characterization mode involves pulsing the lightsource in the heart rate monitor at a second frequency and detectinglight from the light source at the second frequency. In someembodiments, the second frequency is greater than the first frequency.

In some embodiments, the operation of determining the responsecharacteristic of the user's skin involves determining an intensitylevel and/or pattern of two or more light pulses detected at the secondfrequency. In some embodiments, the succession of light pulses includessome light pulses having variable intensity and others having constantintensity.

In some embodiments, the succession of light pulses includes at leasttwo light pulses of variable intensity. In some embodiments, thesuccession of light pulses includes at least four light pulses ofvariable intensity. In some embodiments, the succession of light pulsesemitted in the skin characterization mode include at least two lightpulses of variable intensity. The operation of determining a responsecharacteristic of the user's skin in (c) involves determining a functionor characteristic of the intensity variation of light from the lightpulses detected in (b). The function or characteristic of the intensityvariation is the response characteristic of the user's skin used toadjust the gain and/or light emission intensity of the heart ratemonitor operating in a first mode.

In some embodiments, determining the function or characteristic involvesdetermining a slope of the intensity variation of light from the lightpulses detected in (b).

In some embodiments, adjusting the heart rate monitor's gain and/orlight emission intensity for operating in the first mode involvesreducing the emission intensity.

In some embodiments, the wearable fitness monitoring device includes amotion detecting sensor. In some embodiments, the motion detectingsensor includes an accelerometer, a magnetometer, an altimeter, a GPSdetector, a gyroscope, or a combination of any of these.

Some embodiments provide a method of operating a heart rate monitor of awearable fitness monitoring device, the heart rate monitor having alight source and a light detector. The method involves adjusting theheart rate monitor's operation(s) based on a user's skin characteristicsto improve performance. The method involves: (a) operating the heartrate monitor in a first mode while also operating in a skincharacterization mode for determining a characteristic of a user's skin.The first mode is configured to determine one or more characteristics ofthe user's heartbeat waveform. The skin characterization mode operationinvolves generating data points representing emission intensity from thelight source and corresponding detection levels from the light detector.The method further involves: (b) fitting the data points of the skincharacterization mode to a mathematical relationship relating lightsource emission intensity to light detector detection level; (c) usingthe mathematical relationship to determine a light source emissionintensity setting that provides a pre-determined light detectordetection level identified as providing good heart rate monitorperformance; and (d) adjusting the light source emission intensity tosaid setting determined in (c) for operating in the first mode.

In some embodiments, the mathematical relationship is linear. In someembodiments, the pre-determined light detector detection level waspreviously determined to have a high signal to noise ratio. In someembodiments, the method further involves, prior to (b), determining aslope of a line fitting the data points representing emission intensityfrom the light source and corresponding detection levels from the lightdetector; and setting the light source emission intensity for operatingin the first mode based on the determined slope and pre-set values ofemission intensity levels.

In some embodiments, the first mode and the skin characterization modeare performed concurrently. In some embodiments, operating in the firstmode and operating in the skin characterization mode concurrentlyinvolves periodically determining a response characteristic of theuser's skin while continuously operating in the first mode. In someembodiments, the skin characterization mode occurs no more than about50% of the time.

In some embodiments, operating in the first mode involves pulsing thelight source in the heart rate monitor at a first frequency anddetecting light from the light source, after the light has interactedwith the user's skin, at the first frequency. In some embodiments,operating in the skin characterization mode involves pulsing a lightsource in the heart rate monitor at a second frequency and detectinglight from the light source, after the light has interacted with theuser's skin, at the second frequency. In some embodiments, the secondfrequency is greater than the first frequency.

In some embodiments, operating in the skin characterization mode furtherinvolves determining an intensity level and/or pattern of two or morelight pulses, after the light has interacted with the user's skin,detected at the second frequency.

In some embodiments, operating the heart rate monitor in the skincharacterization mode involves emitting a succession of light pulses,and wherein some of the light pulses have variable intensity and otherlight pulses having constant intensity compared to one another.

In some embodiments, operating the heart rate monitor in the skincharacterization mode involves emitting a succession of light pulses. Insome embodiments, at least two of the light pulses have variableintensity compared to one another. In some embodiments, at least four ofthe light pulses have variable intensity compared to one another.

Some embodiments of the disclosure provide a wearable fitness monitoringdevice having a motion sensor configured to provide output correspondingto motion by a user wearing the fitness monitoring device and aphotoplethysmographic (PPG) sensor. The PPG sensor includes (i) aperiodic light source, (ii) a photo detector positioned to receiveperiodic light emitted by the periodic light source after interactingwith a user's skin, and (iii) circuitry determining a user's heart ratefrom an output of the photo detector. In some embodiments, the periodiclight source includes two periodic light sources straddling the photodetector. In some embodiments, the photoplethysmographic sensor furtherincludes a housing having a recess in which the photo detector isdisposed. In some embodiments, the housing of the photoplethysmographicsensor further includes a second recess in which the periodic lightsource is disposed. In some embodiments, the housing of thephotoplethysmographic sensor protrudes at least about 1 mm above a basesurface of the wearable fitness monitoring device and is configured topress against the user's skin when worn.

In some embodiments, the photoplethysmographic sensor further includes aspring configured to resist compression when the protruding housingpresses against the user's skin. In some embodiments, thephotoplethysmographic sensor further includes an IML, film over thephoto detector and the periodic light source. In some embodiments,wherein the periodic light source of the PPG sensor is an LED.

In many embodiments, wearable fitness monitoring devices are configuredto perform features and operations associated with various methodsdescribed elsewhere herein.

Some embodiments of the disclosure provide a wearable fitness monitoringdevice having a motion sensor, a PPG sensor, and a control logic. ThePPG sensor includes (i) a periodic light source, (ii) a photo detectorpositioned to receive periodic light emitted by the periodic lightsource after interacting with a user's skin, and (iii) circuitrydetermining a user's heart rate from an output of the photo detector.The control logic is configured to: (a) operate the heart rate monitorin a first mode while also operating in a second mode configured todetect near proximity of the wearable fitness monitoring device to auser's skin, where the first mode is configured to determine one or morecharacteristics of a user's heartbeat waveform when the wearable fitnessmonitoring device is in near proximity to the user; (b) from informationcollected in the second mode, determine that the heart rate monitor isnot proximate to the user's skin; and (c) in response to determiningthat the heart rate monitor is not proximate to the user's skin, endoperating the heart rate monitor in the first mode. In some embodiments,operating the heart rate monitor in the second mode involves pulsing alight source in the heart rate monitor at a second mode frequency anddetecting light from the light source at the second mode frequency. Insome embodiments, operating the heart rate monitor in the first modeinvolves pulsing the light source in the heart rate monitor at a firstmode frequency and detecting light from the light source at the firstmode frequency.

In some embodiments, the control logic of the wearable fitnessmonitoring device is configured to: (a) detect motion of the wearablefitness monitoring device using the motion detecting sensor; (b) inresponse to detecting the motion in (a), operate the heart rate monitorin a worn detection mode configured to detect near proximity of thewearable fitness monitoring device to a user's skin; and (c) upondetermining via the worn detection mode that the wearable fitnessmonitoring device is proximate to the user's skin, operate the heartrate monitor in a first mode configured to determine one or morecharacteristics of the user's heartbeat waveform.

In other embodiments, the control logic of the wearable fitnessmonitoring device is configured to: (a) pulse a light source in theheart monitor in a skin characterization mode by emitting a successionof light pulses, at least some having variable intensity with respect toone another; (b) detect a variation in intensity of light from the lightpulses emitted in the skin characterization mode after the light hasinteracted with the user's skin; (c) determine a response characteristicof the user's skin from the variation in intensity of light detected in(b); and (d) use the response characteristic of the user's skin toadjust a gain and/or light emission intensity of the heart rate monitoroperating in a first mode for detecting one or more characteristics ofthe user's heartbeat waveform.

In further embodiments, the control logic of the wearable fitnessmonitoring device is configured to: (a) operate the heart rate monitorin a first mode while also operating in a skin characterization mode fordetermining a characteristic of a user's skin. The first mode isconfigured to determine one or more characteristics of the user'sheartbeat waveform, and the skin characterization mode involvesgenerating data points representing emission intensity from the lightsource and corresponding detection levels from the light detector. Thecontrol logic is further configured to: (b) fit the data points of theskin characterization mode to a mathematical relationship relating lightsource emission intensity to light detector detection level; (c) use themathematical relationship to determine a light source emission intensitysetting that provides a pre-determined light detector detection levelidentified as providing good heart rate monitor performance; and (d)adjust the light source emission intensity to said setting determined in(c) for operating in the first mode.

BRIEF DESCRIPTION OF DRAWINGS

The various implementations disclosed herein are illustrated by way ofexample, and not by way of limitation, in the figures of theaccompanying drawings, in which like reference numerals may refer tosimilar elements.

FIG. 1 illustrates an example portable monitoring device which enablesuser interaction via a user interface.

FIG. 2A illustrates an example portable monitoring device which may besecured to the user through the use of a band.

FIG. 2B provides a view of the example portable monitoring device ofFIG. 2A which shows the skin-facing portion of the device.

FIG. 2C provides a cross-sectional view of the portable monitoringdevice of FIG. 2A.

FIG. 3A provides a cross sectional view of a sensor protrusion of anexample portable monitoring device.

FIG. 3B depicts a cross sectional view of a sensor protrusion of anexample portable monitoring device; this protrusion is similar to thatpresented in FIG. 3A with the exception that the light sources andphotodetector are placed on a flat and/or rigid PCB.

FIG. 3C provides another cross-sectional view of an example PPG sensorimplementation.

FIG. 4A illustrates an example of one potential PPG light source andphotodetector geometry.

FIGS. 4B and 4C illustrate examples of a PPG sensor having aphotodetector and two LED light sources.

FIG. 5 Illustrates an example of an optimized PPG detector that has aprotrusion with curved sides so as not to discomfort the user.

FIG. 6A illustrates an example of a portable monitoring device having aband; optical sensors and light emitters may be placed on the band.

FIG. 6B illustrates an example of a portable biometric monitoring devicehaving a display and wristband. Additionally, optical PPG (e.g., heartrate) detection sensors and/or emitters may be located on the side ofthe biometric monitoring device. In one embodiment, these may be locatedin side-mounted buttons.

FIG. 7 depicts a user pressing the side of a portable biometricmonitoring device to take a heart rate measurement from a side-mountedoptical heart rate detection sensor. The display of the biometricmonitoring device may show whether or not the heart rate has beendetected and/or display the user's heart rate.

FIG. 8 illustrates functionality of an example biometric monitoringdevice smart alarm feature.

FIG. 9 illustrates an example of a portable biometric monitoring devicethat changes how it detects a user's heart rate based on how muchmovement the biometric monitoring device is experiencing.

FIG. 10 illustrates an example of a portable biometric monitoring devicethat has a bicycle application on it that may display bicycle speedand/or pedaling cadence, among other metrics.

FIG. 11A illustrates an example block diagram of a PPG sensor which hasa light source, light detector, ADC, processor, DAC/GPIOs, and lightsource intensity and on/off control.

FIG. 11B illustrates an example block diagram of a PPG sensor that issimilar to that of FIG. 11A which additionally uses a sample-and-holdcircuit as well as analog signal conditioning.

FIG. 11C illustrates an example block diagram of a PPG sensor that issimilar to that of FIG. 11A which additionally uses a sample-and-holdcircuit.

FIG. 11D illustrates an example block diagram of a PPG sensor havingmultiple switchable light sources and detectors, light sourceintensity/on and off control, and signal conditioning circuitry.

FIG. 11E illustrates an example block diagram of a PPG sensor which usessynchronous detection. To perform this type of PPG detection, it has ademodulator.

FIG. 11F illustrates an example block diagram of a PPG sensor which, inaddition to the features of the sensor illustrated in FIG. 11A, has adifferential amplifier.

FIG. 11G illustrates an example block diagram of a PPG sensor which hasthe features of the PPG sensors shown in FIGS. 11A-KKF.

FIG. 12A illustrates an example of a portable biometric monitoringdevice having a heart rate or PPG sensor, motion sensor, display,vibromotor, and communication circuitry which is connected to aprocessor.

FIG. 12B illustrates an example of a portable biometric monitoringdevice having a heart rate or PPG sensor, motion sensor, display,vibromotor, location sensor, altitude sensor, skin conductance/wetsensor and communication circuitry which is connected to a processor.

FIG. 12C illustrates an example of a portable biometric monitoringdevice having physiological sensors, environmental sensors, and locationsensors connected to a processor.

FIG. 13A illustrates an example of the use of a motion signal and anoptical PPG signal to measure a heart rate.

FIG. 13B illustrates another example of the use of a motion signal andan optical PPG signal to measure heart rate.

FIG. 14A illustrates an example of a sensor which has an analogconnection to a sensor processor.

FIG. 14B illustrates an example of a sensor which has an analogconnection to a sensor processor which, in turn, has a digitalconnection to an application processor.

FIG. 14C illustrates an example of a sensor device which has one ormultiple sensors connected to an application processor.

FIG. 14D illustrates an example of a sensor device which has one ormultiple sensors connected to sensor processors which, in turn, areconnected to an application processor.

FIG. 15A illustrates an example of a swim detection algorithm using asequential algorithm flow.

FIG. 15B illustrates an example of a swim detection algorithm which usesa parallel algorithm flow.

FIG. 15C illustrates an example of a swim detection algorithm which usesa hybrid of sequential and parallel algorithm flow.

FIG. 15D illustrates an example of a swim detection algorithm which usesa hybrid of sequential and parallel algorithm flow.

FIG. 16A illustrates an example schematic of a sample-and-hold circuitand differential/instrumentation amplifier which may be used in PPGsensing.

FIG. 16B illustrates an example schematic of a circuit for a PPG sensorusing a controlled current source to offset “bias” current prior to atransimpedance amplifier

FIG. 16C illustrates an example schematic of a circuit for a PPG sensorusing a sample-and-hold circuit for current feedback applied tophotodiode (prior to a transimpedance amplifier).

FIG. 16D illustrates an example schematic of a circuit for a PPG sensorusing a differential/instrumentation amplifier with ambient lightcancellation functionality.

FIG. 16E illustrates an example schematic of a circuit for a PPG sensorusing a photodiode offset current generated dynamically by a DAC.

FIG. 16F illustrates an example schematic of a circuit for a PPG sensorusing a photodiode offset current generated dynamically by a controlledvoltage source.

FIG. 16G illustrates an example schematic of a circuit for a PPG sensorincluding ambient light removal functionality using a “switchedcapacitor” method.

FIG. 16H illustrates an example schematic of a circuit for a PPG sensorthat uses a photodiode offset current generated by a constant currentsource (this may also be done using a constant voltage source and aresistor).

FIG. 16I illustrates an example schematic of a circuit for a PPG sensorthat includes ambient light removal functionality and differencingbetween consecutive samples.

FIG. 16J illustrates an example schematic of a circuit for ambient lightremoval and differencing between consecutive samples.

FIG. 17A shows a schematic diagram of a process that uses a lightprobing mechanism to determine whether the heart rate monitor is worn(“on-wrist”) or unworn (“off-wrist”).

FIG. 17B shows a schematic diagram of a process that uses separate lightprobing mechanisms for off-wrist detection to exit PPG heart ratemonitoring and for on-wrist detection to enter PPG heart ratemonitoring.

FIG. 18A shows a process flowchart for a wearable fitness monitoringdevice having the heart rate monitor operates in different modes inenergy efficient ways according to some embodiments.

FIG. 18B shows another process flowchart for operating a wearablefitness monitoring device having a heart rate monitor according to someembodiments starting with concurrent operation of a first mode fordetecting heart signals and a second mode for detecting an unworn state.

FIG. 18C shows a cartoon of light pulses that are used to provide datafor heart rate vs. the light pulses for probing proximity of the user'sbody in some embodiments.

FIG. 18D shows another cartoon of light pulses that can be used toprovide data for heart rate vs. the light pulses for probing proximityof the user's body in some embodiments.

FIG. 19A shows two relationship between light intensity emitted by alight source of a heart rate monitor vs. the signal detected by aphotodetector of the heart rate monitor.

FIG. 19B depicts the temporal modulation of the TIA signal as a resultof heart beats.

FIG. 19C shows flowchart for a process of operating a heart rate monitorof a wearable fitness monitoring device by adjusting light emissionpower and/or light detection gain of the heart rate monitor.

FIG. 19D shows light pulse signal patterns that may be used to regulatea heart rate monitor's light source intensity and/or light detectiongain.

FIGS. 19E and 19F respectively show linear and non-linear mathematicalrelationships between emitted intensity and detected intensity fordifferent skin characteristics.

DETAILED DESCRIPTION

This disclosure is directed at biometric monitoring devices (which mayalso be referred to herein and in any references incorporated byreference as “wearable fitness monitoring device,” “biometric trackingdevices,” “personal health monitoring devices,” “portable monitoringdevices,” “portable biometric monitoring devices,” “biometric monitoringdevices,” or the like), which may be generally described as wearabledevices, typically of a small size, that are designed to be wornrelatively continuously by a person. When worn, such biometricmonitoring devices gather data regarding activities performed by thewearer or the wearer's physiological state. Such data may include datarepresentative of the ambient environment around the wearer or thewearer's interaction with the environment, e.g., motion data regardingthe wearer's movements, ambient light, ambient noise, air quality, etc.,as well as physiological data obtained by measuring variousphysiological characteristics of the wearer, e.g., heart rate,perspiration levels, etc.

Biometric monitoring devices have been described in U.S. patentapplication Ser. No. 14/507,173, U.S. Pat. Nos. 8,948,832, 8,954,135,U.S. Provisional Patent Application Nos. 61/662,961 and 61/752,826,61/830,600, 61/946,439, 61/955,045, 61/973,614, 62/001,624, and62/001,585, all of which are hereby incorporated by reference herein intheir entireties.

Biometric monitoring devices, as mentioned above, are typically small insize so as to be unobtrusive for the wearer. Fitbit offers severalvarieties of biometric monitoring devices that are all quite small andvery light, e.g., the Fitbit Flex is a wristband with an insertablebiometric monitoring device that is about 0.5″ wide by 1.3″ long by0.25″ thick. Biometric monitoring devices are typically designed to beable to be worn without discomfort for long periods of time and to notinterfere with normal daily activity.

In some cases, a biometric monitoring device may leverage other devicesexternal to the biometric monitoring device, e.g., an external heartrate monitor in the form of an EKG sensor on a chest strap may be usedto obtain heart rate data or a GPS receiver in a smartphone may be usedto obtain position data. In such cases, the biometric monitoring devicemay communicate with these external devices using wired or wirelesscommunications connections. The concepts disclosed and discussed hereinmay be applied to both stand-alone biometric monitoring devices as wellas biometric monitoring devices that leverage sensors or functionalityprovided in external devices, e.g., external sensors, sensors orfunctionality provided by smartphones, etc.

In general, the concepts discussed herein may be implemented instand-alone biometric monitoring devices as well as, when appropriate,biometric monitoring devices that leverage external devices.

It is to be understood that while the concepts and discussion includedherein are presented in the context of biometric monitoring devices,these concepts may also be applied in other contexts as well if theappropriate hardware is available. For example, many modern smartphonesinclude motion sensors, such as accelerometers, that are normallyincluded in biometric monitoring devices, and the concepts discussedherein may, if appropriate hardware is available in a device, beimplemented in that device. In effect, this may be viewed as turning thesmartphone into some form of biometric monitoring device (although onethat is larger than a typical biometric monitoring device and that maynot be worn in the same manner). Such implementations are also to beunderstood to be within the scope of this disclosure.

The functionality discussed herein may be provided using a number ofdifferent approaches. For example, in some implementations a processormay be controlled by computer-executable instructions stored in memoryso as to provide functionality such as is described herein. In otherimplementations, such functionality may be provided in the form of anelectrical circuit. In yet other implementations, such functionality maybe provided by a processor or processors controlled bycomputer-executable instructions stored in a memory coupled with one ormore specially-designed electrical circuits. Various examples ofhardware that may be used to implement the concepts outlined hereininclude, but are not limited to, application specific integratedcircuits (ASICs), field-programmable gate arrays (FPGAs), andgeneral-purpose microprocessors coupled with memory that storesexecutable instructions for controlling the general-purposemicroprocessors.

Standalone biometric monitoring devices may be provided in a number ofform factors and may be designed to be worn in a variety of ways. Insome implementations, a biometric monitoring device may be designed tobe insertable into a wearable case or into multiple, different wearablecases, e.g., a wristband case, a belt-clip case, a pendant case, a caseconfigured to be attached to a piece of exercise equipment such as abicycle, etc. Such implementations are described in more detail in, forexample, U.S. patent application Ser. No. 14/029,764, filed Sep. 17,2013, which is hereby incorporated by reference for such purpose. Inother implementations, a biometric monitoring device may be designed tobe worn in only one manner, e.g., a biometric monitoring device that isintegrated into a wristband in a non-removable manner may be intended tobe worn only on a person's wrist (or perhaps ankle).

Portable biometric monitoring devices according to embodiments andimplementations described herein may have shapes and sizes adapted forcoupling to (e.g., secured to, worn, borne by, etc.) the body orclothing of a user. An example of a portable biometric monitoringdevices is shown in FIG. 1; the example portable monitoring device mayhave a user interface, processor, biometric sensor(s), memory,environmental sensor(s) and/or a wireless transceiver which maycommunicate with a client and/or server. An example of a wrist-wornportable biometric monitoring device is shown in FIGS. 2A through 2C.This device may have a display, button(s), electronics package, and/oran attachment band. The attachment band may be secured to the userthrough the use of hooks and loops (e.g., Velcro), a clasp, and/or aband having memory of its shape, e.g., through the use of a spring metalband. In FIG. 2B, a sensor protrusion and recess for mating a chargerand/or data transmission cable can be seen. In FIG. 2C, a cross-sectionthrough the electronics package is shown. Of note are the sensorprotrusion, main PCB board, and display.

Portable biometric monitoring devices may collect one or more types ofphysiological and/or environmental data from embedded sensors and/orexternal devices and communicate or relay such information to otherdevices, including devices capable of serving as an Internet-accessibledata sources, thus permitting the collected data to be viewed, forexample, using a web browser or network-based application. For example,while the user is wearing a biometric monitoring device, the biometricmonitoring device may calculate and store the user's step count usingone or more biometric sensors. The biometric monitoring device may thentransmit data representative of the user's step count to an account on aweb service (e.g., www.fitbit.com), computer, mobile phone, or healthstation where the data may be stored, processed, and visualized by theuser. Indeed, the biometric monitoring device may measure or calculate aplurality of other physiological metrics in addition to, or in place of,the user's step count. These include, but are not limited to, energyexpenditure, e.g., calorie burn, floors climbed and/or descended, heartrate, heart rate variability, heart rate recovery, location and/orheading, e.g., through GPS, GLONASS, or a similar system, elevation,ambulatory speed and/or distance traveled, swimming lap count, swimmingstroke type and count detected, bicycle distance and/or speed, bloodpressure, blood glucose, skin conduction, skin and/or body temperature,muscle state measured via electromyography, brain activity as measuredby electroencephalography, weight, body fat, caloric intake, nutritionalintake from food, medication intake, sleep periods, e.g., clock time,sleep phases, sleep quality and/or duration, pH levels, hydrationlevels, respiration rate, and other physiological metrics. The biometricmonitoring device may also measure or calculate metrics related to theenvironment around the user such as barometric pressure, weatherconditions (e.g., temperature, humidity, pollen count, air quality,rain/snow conditions, wind speed), light exposure (e.g., ambient light,UV light exposure, time and/or duration spent in darkness), noiseexposure, radiation exposure, and magnetic field. Furthermore, thebiometric monitoring device or the system collecting the data streamsfrom the biometric monitoring device may calculate metrics derived fromsuch data. For example, the device or system may calculate the user'sstress and/or relaxation levels through a combination of heart ratevariability, skin conduction, noise pollution, and sleep quality. Inanother example, the device or system may determine the efficacy of amedical intervention, e.g., medication, through the combination ofmedication intake, sleep data, and/or activity data. In yet anotherexample, the biometric monitoring device or system may determine theefficacy of an allergy medication through the combination of pollendata, medication intake, sleep and/or activity data. These examples areprovided for illustration only and are not intended to be limiting orexhaustive. Further embodiments and implementations of sensor devicesmay be found in U.S. patent application Ser. No. 13/156,304, titled“Portable Biometric Monitoring Devices and Methods of Operating Same”filed Jun. 8, 2011 and U.S. Patent Application 61/680,230, titled“Fitbit Tracker” filed Aug. 6, 2012, which are both hereby incorporatedherein by reference in their entireties.

Physiological Sensors

Biometric monitoring devices as discussed herein may use one, some orall of the following sensors to acquire physiological data, including,but not limited to, the physiological data outlined in the table below.All combinations and permutations of physiological sensors and/orphysiological data are intended to fall within the scope of thisdisclosure. Biometric monitoring devices may include but are not limitedto types of one, some, or all of the sensors specified below for theacquisition of corresponding physiological data; indeed, other type(s)of sensors may also or alternatively be employed to acquire thecorresponding physiological data, and such other types of sensors arealso intended to fall within the scope of the present disclosure.Additionally, the biometric monitoring device may derive thephysiological data from the corresponding sensor output data, but is notlimited to the number or types of physiological data that it couldderive from said sensor.

Physiological Sensors Physiological data acquired Optical Heart Rate,Heart Reflectometer Rate Variability Example SpO₂ (Saturation ofSensors: Peripheral Oxygen) Light emitter and receiver Respiration Multior single LED and photo diode Stress arrangement Blood pressureWavelength tuned for specific physiological Arterial Stiffness signalsBlood glucose levels Synchronous detection/ Blood volume amplitudemodulation Heart rate recovery Cardiac health Motion Detector Activitylevel detection Example Sensors: Sitting/standing detection Inertialsensors, Gyroscopic Fall detection sensors, and/or Accelerometers GPSSkin Temperature Stress EMG (eletromyographic sensor) Muscle tension EKGor ECG (electrocardiographic sensor) Heart Rate Example Sensors: HeartRate Variability Single-lead ECG or EKG Heart Rate Recovery Dual-leadECG or EKG Stress Cardiac health Magnetometer Activity level based onrotation Laser Doppler Power Meter Ultrasonic Sensor Blood flow AudioSensor Heart Rate Heart Rate Variability Heart Rate Recovery Laughdetection Respiration Respiration type, e.g., snoring, breathing,breathing problems (such as sleep apnea) User's voice Strain gauge HeartRate Example: Heart Rate Variability In a wrist band StressWet/Immersion Sensor Stress Example Sensor: Swimming detection Galvanicskin response Shower detection

In one example embodiment, the biometric monitoring device may includean optical sensor to detect, sense, sample and/or generate data that maybe used to determine information representative of, for example, stress(or level thereof), blood pressure, and/or heart rate of a user. (See,for example, FIGS. 2A through 3C and 11A through KKG). In suchembodiments, the biometric monitoring device may include an opticalsensor having one or more light sources (LED, laser, etc.) to emit oroutput light into the user's body, as well as light detectors(photodiodes, phototransistors, etc.) to sample, measure and/or detect aresponse or reflection of such light from the user's body and providedata used to determine data that is representative of stress (or levelthereof), blood pressure, and/or heart rate of a user (e.g., such as byusing photoplethysmography).

In one example embodiment, a user's heart rate measurement may betriggered by criteria determined by one or more sensors (or processingcircuitry connected to them). For instance, when data from a motionsensor(s) indicates a period of stillness or of little motion, thebiometric monitoring device may trigger, acquire, and/or obtain a heartrate measurement or data. (See, for example, FIGS. 9, 12A, and 12B).

FIG. 12A illustrates an example of a portable biometric monitoringdevice having a heart rate or PPG sensor, motion sensor, display,vibromotor, and communication circuitry which is connected to aprocessor.

FIG. 12B illustrates an example of a portable biometric monitoringdevice having a heart rate or PPG sensor, motion sensor, display,vibromotor, location sensor, altitude sensor, skin conductance/wetsensor and communication circuitry which is connected to a processor.

In one embodiment, when the motion sensor(s) indicate user activity ormotion (for example, motion that is not suitable or optimum to trigger,acquire, and/or obtain desired heart rate measurement or data (forexample, data used to determine a user's resting heart rate)), thebiometric monitoring device and/or the sensor(s) employed to acquireand/or obtain a desired heart rate measurement or data may be placed in,or remain in, a low power state. Since heart rate measurements takenduring motion may be less reliable and may be corrupted by motionartifacts, it may be desirable to decrease the frequency with whichheart rate data samples are collected (thus decreasing power usage) whenthe biometric monitoring device is in motion.

In another embodiment, a biometric monitoring device may employ data(for example, from one or more motion sensors) indicative of useractivity or motion to adjust or modify characteristics of triggering,acquiring, and/or obtaining desired heart rate measurements or data (forexample, to improve robustness to motion artifact). For instance, if thebiometric monitoring device receives data indicative of user activity ormotion, the biometric monitoring device may adjust or modify thesampling rate and/or resolution mode of sensors used to acquire heartrate data (for example, where the amount of user motion exceeds acertain threshold, the biometric monitoring device may increase thesampling rate and/or increase the sampling resolution mode of sensorsemployed to acquire heart rate measurement or data.) Moreover, thebiometric monitoring device may adjust or modify the sampling rateand/or resolution mode of the motion sensor(s) during such periods ofuser activity or motion (for example, periods where the amount of usermotion exceeds a certain threshold). In this way, when the biometricmonitoring device determines or detects such user activity or motion,the biometric monitoring device may place the motion sensor(s) into ahigher sampling rate and/or higher sampling resolution mode to, forexample, enable more accurate adaptive filtering of the heart ratesignal. (See, for example, FIG. 9).

FIG. 9 illustrates an example of a portable biometric monitoring devicethat changes how it detects a user's heart rate based on how muchmovement the biometric monitoring device is experiencing. In the casewhere there is motion detected (e.g., through the use of anaccelerometer), the user may be considered by the biometric monitoringdevice to be “active” and high-sampling-rate heart rate detection mayoccur to reduce motion artifacts in the heart rate measurement. Thisdata may be saved and/or displayed. In the case that the user isdetermined by the biometric monitoring device to not be moving (or to berelatively sedentary), low-sampling-rate heart rate detection (whichdoes not consume as much power) may be adequate to measure a heart rateand may thus be used.

Notably, where a biometric monitoring device employs optical techniquesto acquire heart rate measurements or data, e.g., by usingphotoplethysmography, a motion signal may be employed to determine orestablish a particular approach or technique to data acquisition ormeasurement by the heart rate sensor (e.g., synchronous detection ratherthan a non-amplitude-modulated approach) and/or analysis thereof. (See,for example, FIG. 11E). In this way, the data which is indicative of theamount of user motion or activity may cause the biometric monitoringdevice to establish or adjust the type or technique of data acquisitionor measurement used by an optical heart rate sensor or sensors.

For example, in one embodiment, a biometric monitoring device (orheart-rate measurement technique as disclosed herein) may adjust and/orreduce the sampling rate of optical heart rate sampling when motiondetector circuitry detects or determines that the biometric monitoringdevice wearer's motion is below a threshold (for example, if thebiometric monitoring device determines the user is sedentary or asleep).(See, for example, FIG. 9). In this way, the biometric monitoring devicemay control its power consumption. For example, the biometric monitoringdevice may reduce power consumption by reducing the sensor samplingrate—for instance, the biometric monitoring device may sample the heartrate (via the heart rate sensor) once every 10 minutes, or 10 secondsout of every 1 minute. Notably, the biometric monitoring device may, inaddition thereto or in lieu thereof, control power consumption viacontrolling data processing circuitry analysis and/or data analysistechniques in accordance with motion detection. As such, the motion ofthe user may impact the heart rate data acquisition parameters and/ordata analysis or processing thereof.

Motion Artifact Suppression in Heart Rate Sensors

As discussed above, the raw heart rate signal measured by a PPG sensormay be improved by using one or more algorithms to remove motionartifacts. Movement of the user (for determining motion artifacts) maybe measured using sensors including, but not limited to, accelerometers,gyroscopes, proximity detectors, magnetometers, etc. The goal of suchalgorithms is to remove components os the PPG signal attributable tomovement (movement artifacts) using the movement signal captured fromthe other sensors as a guide. In one embodiment the movement artifactsin the PPG signal may be removed using an adaptive filter based on ahybrid Kalman filter and a least mean square filter or a recursive leastsquares filter. The heart rate may then be extracted from thecleaned/filtered signal using a peak counting algorithm or a powerspectral density estimation algorithm. Alternatively, a Kalman filter orparticle filter may be used to remove such movement artifacts.

Another approach that may be used to calculate the heart rate frequencyis to create a model of the heart rate signal as Y=Y_(dc)+Σa_(k)*coskθ+b_(k)*sin kθ, where k is the order of harmonic components, and θ is amodel parameter for heart rate. This model may then be fit to the signalusing either an extended Kalman filter or a particle filter. This modelexploits the fact that the signal is not sinusoidal so contains powerboth at the fundamental harmonic as well as multiple additionalharmonics.

Alternately, the signal may be modeled as Y=Y_(dc)+Σa_(k)*sin(k*w_(motion)t+θ)+Σb_(k)*sin(k*w_(HR)t+ϕ), where w_(motion) is estimateddirectly from the accelerometer signal (or another motion sensorsignal).

Ambient Light and Skin Color

Ambient light and skin color may make it difficult to extract a user'sheart rate from a PPG signal. The effect of ambient light may be reducedby subtracting a value of the received detected light signal when thePPG light source is off from the value of the received detected lightsignal when the PPG light source is on (assuming that both signals areobtained in close temporal proximity to each other).

The effect of skin color may be reduced by changing the intensity of thePPG light source, the wavelength of the light emitted from the lightsource, and/or by using the ratio or difference of received signalcorresponding to two different wavelengths. Skin color may be determinedby using user input (e.g. the user entering their skin color), an imageof the person's face, etc., and may then subsequently be used tocalibrate the algorithm, light source brightness, light sourcewavelength, and the receiver gain. The effect of skin color (andtightness with which the user is wearing the device) on the raw PPGsignal may also be measured by sending in a signal of known amplitude tothe light source(s) and then measuring the received signal from thephotodetector(s). Such a signal may be sent for a prolonged period oftime (so as to capture data through multiple expected heart beats) andthen averaged to produce a steady-state data set that is not heart-ratedependent. This amplitude may then be compared to a set of values storedin a table to determine algorithm calibration, transmitter amplitude andthe receiver gain.

Heart Rate Estimate Improvement Using Heuristics

After getting an initial estimate of the heart rate (e.g. by peakcounting of a power spectral density estimation), it may be useful toapply bounds on the allowable rates for heart rate. These bounds may beoptimized on a per-user basis since each user will have a unique heartrate profile. For example, the sedentary rate of each user may beestimated when they are stationary and this may be used as a lower boundwhen the user is walking. Similarly, half the frequency of walking ascalculated from the pedometer may serve as a good lower bound for theexpected heart rate.

The heart rate algorithm may be tailored for each user and may learn theheart rate profile of the user and adapt to the user's behaviors and/orcharacteristics so as to perform better with time. For example, thealgorithm may set bounds on the heart rate expected during a particularphysical activity or rate of walking based on historical data from thatuser. This may help provide better results when the heart rate data iscorrupted by noise and/or motion artifacts.

HR Quality Metric

In another example embodiment, a signal quality metric of the heartrate/PPG signal may be used to provide a quantification of theaccuracy/precision of the signal being generated. Depending on thevalues of this metric, the algorithm that determines what the user'sheart rate (or other PPG-derived metric such as respiration) is may takecertain actions, including asking the user to tighten the watch band,ignoring certain portions of collected heart-rate data (e.g. sections ofdata that have a low quality metric), and weighting certain portions ofthe heart-rate data (e.g., data with a higher quality metric may beweighted more heavily when the heart rate is being calculated).

In one embodiment, the signal quality metric may be derived as follows:make a scatter plot where the x-axis is time, and the y-axis is thefrequency of a peak in the PPG signal at that given instant in time. Anissue to be overcome using this strategy is that there may be multipleand/or zero peaks at a given instant in time. A best fit line capturesthe linear relationship in this scatter plot. A high quality signalshould have a set of peaks that fit well to a line (in a short timespan), whereas a bad signal will have a set of peaks that are not welldescribed by a line. Therefore, the quality of the fit to the lineprovides a good metric for the quality of the PPG signal itself.

Sedentary, Sleep, and Active Classified Metrics

In yet another example embodiment, the biometric monitoring device mayemploy sensors to calculate heart rate variability when the devicedetermines the user to be sedentary or asleep. Here, the biometricmonitoring device may operate the sensors in a higher-rate sampling mode(relative to non-sedentary periods or periods of user activity thatexceed a predetermined threshold) to calculate heart rate variability.The biometric monitoring device (or an external device) may employ heartrate variability as an indicator of cardiac health or stress.

Indeed, in some embodiments, the biometric monitoring device may measureand/or determine the user's stress level and/or cardiac health when theuser is sedentary and/or asleep (for example, as detected and/ordetermined by the biometric monitoring device). Some embodiments of abiometric monitoring device of the present disclosure may determine theuser's stress level, health state (e.g., risk, onset, or progression offever or cold), and/or cardiac health using sensor data that isindicative of the heart rate variability, galvanic skin response, skintemperature, body temperature, and/or heart rate. In this way,processing circuitry of the biometric monitoring device may determineand/or track the user's “baseline” stress levels over time and/orcardiac “health” over time. In another embodiment, the device maymeasure a physiologic parameter of the user during one or more periodswhere the user is motionless (or the user's motion is below apredetermined threshold), such as when the user is sitting, lying down,asleep, or in a sleep stage (e.g., deep sleep). Such data may also beemployed by the biometric monitoring device as a “baseline” forstress-related parameters, health-related parameters (e.g., risk oronset of fever or cold), cardiac health, heart rate variability,galvanic skin response, skin temperature, body temperature and/or heartrate.

Sleep Monitoring

In some embodiments, the biometric monitoring device may automaticallydetect or determine when the user is attempting to go to sleep, isentering sleep, is asleep, and/or is awoken from a period of sleep. Insuch embodiments, the biometric monitoring device may employphysiological sensors to acquire data and the data processing circuitryof the biometric monitoring device may correlate a combination of heartrate, heart rate variability, respiration rate, galvanic skin response,motion, skin temperature, and/or body temperature data collected fromsensors of the biometric monitoring device to detect or determine if theuser is attempting to go to sleep, is entering sleep, is asleep, and/oris awoken from a period of sleep. In response, the biometric monitoringdevice may, for example, acquire physiological data (of the types, andin the manners, as described herein) and/or determine physiologicalconditions of the user (of the types, and in the manners, as describedherein). For example, a decrease or cessation of user motion combinedwith a reduction in user heart rate and/or a change in heart ratevariability may indicate that the user has fallen asleep. Subsequentchanges in heart rate variability and galvanic skin response may then beused by the biometric monitoring device to determine transitions of theuser's sleep state between two or more stages of sleep (for example,into lighter and/or deeper stages of sleep). Motion by the user and/oran elevated heart rate and/or a change in heart rate variability may beused by the biometric monitoring device to determine that the user hasawoken.

Real-time, windowed, or batch processing may be used to determine thetransitions between wake, sleep, and sleep stages. For instance, adecrease in heart rate may be measured in a time window where the heartrate is elevated at the start of the window and reduced in the middle(and/or end) of the window. The awake and sleep stages may be classifiedby a hidden Markov model using changes in motion signal (e.g.,decreasing motion intensity), heart rate, heart rate variability, skintemperature, galvanic skin response, and/or ambient light levels. Thetransition points may be determined through a changepoint algorithm(e.g., Bayesian changepoint analysis). The transition between awake andsleep may be determined by observing periods where the user's heart ratedecreases over a predetermined time duration by at least a certainthreshold but within a predetermined margin of the user's resting heartrate (that is observed as, for example, the minimum heart rate of theuser while sleeping). Similarly, the transition between sleep and awakemay be determined by observing an increase in the user's heart rateabove a predetermined threshold of the user's resting heart rate.

In some embodiments, the biometric monitoring device may be onecomponent of a system for monitoring sleep, where the system includes asecondary device configured to communicate with the biometric monitoringdevice and adapted to be placed near the sleeper (e.g., an alarm clock).The secondary device may, in some implementations, have a shape andmechanical and/or magnetic interface to accept the biometric monitoringdevice for safe keeping, communication, and/or charging. However, thesecondary device may also be generic to the biometric monitoring device,e.g., a smartphone that is not specifically designed to physicallyinterface with the biometric monitoring device. The communicationbetween the biometric monitoring device and the secondary device may beprovided through wired communication interfaces or through wirelesscommunication interfaces and protocols such as Bluetooth (including, forexample, Bluetooth 4.0 and Bluetooth Low Energy protocols), RFID, NFC,or WLAN. The secondary device may include sensors to assist in sleepmonitoring or environmental monitoring such as, for example, sensorsthat measure ambient light, noise and/or sound (e.g., to detectsnoring), temperature, humidity, and air quality (pollen, dust, CO2,etc.). In one embodiment, the secondary device may communicate with anexternal service such as www.fitbit.com or a server (e.g., a personalcomputer). Communication with the secondary device may be achievedthrough wired (e.g., Ethernet, USB) or wireless (e.g., WLAN, Bluetooth,RFID, NFC, cellular) circuitry and protocols to transfer data to and/orfrom the secondary device. The secondary device may also act as a relayto transfer data to and/or from the biometric monitoring device toand/or from an external service such as www.fitbit.com or other service(e.g., data such as news, social network updates, email, calendarnotifications) or server (e.g., personal computer, mobile phone,tablet). Calculation of the user's sleep data may be performed on one orboth devices or an external service (e.g., a cloud server) using datafrom one or both devices.

The secondary device may be equipped with a display to display dataobtained by the secondary device or data transferred to it by thebiometric monitoring device, the external service, or a combination ofdata from the biometric monitoring device, the secondary device, and/orthe external service. For example, the secondary device may display dataindicative of the user's heart rate, total steps for the day, activityand/or sleep goal achievement, the day's weather (measured by thesecondary device or reported for a location by an external service),etc. In another example, the secondary device may display data relatedto the ranking of the user relative to other users, such as total weeklystep count. In yet another embodiment, the biometric monitoring devicemay be equipped with a display to display data obtained by the biometricmonitoring device, the secondary device, the external service, or acombination of the three sources. In embodiments where the first deviceis equipped with a wakeup alarm (e.g., vibramotor, speaker), thesecondary device may act as a backup alarm (e.g., using an audiospeaker). The secondary device may also have an interface (e.g., displayand buttons or touch screen) to create, delete, modify, or enable alarmson the first and/or the secondary device.

Sensor-Based Standby Mode

In another embodiment, the biometric monitoring device may automaticallydetect or determine whether it is or is not attached to, disposed on,and/or being worn by a user. In response to detecting or determiningthat the biometric monitoring device is not attached to, disposed on,and/or being worn by a user, the biometric monitoring device (orselected portions thereof) may implement or be placed in a low powermode of operation—for example, the optical heart rate sensor and/orcircuitry may be placed in a lower power or sleep mode. For example, inone embodiment, the biometric monitoring device may include one or morelight detectors (photodiodes, phototransistors, etc.). If, at a givenlight intensity setting (for example, with respect to the light emittedby a light source that is part of the biometric monitoring device), oneor more light detectors provides a low return signal, the biometricmonitoring device may interpret the data as indicative of the device notbeing worn. Upon such a determination, the device may reduce its powerconsumption—for example, by “disabling” or adjusting the operatingconditions of the stress and/or heart rate detection sensors and/orcircuitry in addition to other device circuitry or displays (forexample, by reducing the duty cycle of or disabling the light source(s)and/or detector(s), turning off the device display, and/or disabling orattenuating associated circuitry or portions thereof). In addition, thebiometric monitoring device may periodically determine (e.g., once persecond) if the operating conditions of the stress and/or heart ratedetection sensors and/or associated circuitry should be restored to anormal operating condition (for example, light source(s), detector(s)and/or associated circuitry should return to a normal operating mode forheart rate detection). In another embodiment, the biometric monitoringdevice may restore the operating conditions of the stress and/or heartrate detection sensors and/or associated circuitry upon detection of atriggerable event—for example, upon detecting motion of the device (forexample, based on data from one or more motion sensor(s)) and/ordetecting a user input via the user interface (for example, a tap, bumpor swipe interaction with the biometric monitoring device). In somerelated embodiments, the biometric monitoring device may, for powersaving purposes, reduce its default rate of heart rate measurementcollection to, for instance, one measurement per minute while the useris not highly active and the user may have the option of putting thedevice into a mode of operation to generate measurements on demand or ata faster rate (e.g., once per second), for instance, by pushing abutton.

Optical Sensor(s)

In one embodiment, the optical sensors (sources and/or detectors) may bedisposed on an interior or skin-side of the biometric monitoring device(i.e., a side of the biometric monitoring device that contacts, touches,and/or faces the skin of the user (hereinafter “skin-side”)). (See, forexample, FIGS. 2A through 3C). In another embodiment, the opticalsensors may be disposed on one or more sides of the device, includingthe skin-side and one or more sides of the device that face or areexposed to the ambient environment (environmental side). (See, forexample, FIGS. 6A through 7).

FIG. 6A illustrates an example of a portable monitoring device having aband; optical sensors and light emitters may be placed on the band.

FIG. 6B illustrates an example of a portable biometric monitoring devicehaving a display and wristband. Additionally, optical PPG (e.g., heartrate) detection sensors and/or emitters may be located on the side ofthe biometric monitoring device. In one embodiment, these may be locatedin side-mounted buttons.

FIG. 7 depicts a user pressing the side of a portable biometricmonitoring device to take a heart rate measurement from a side-mountedoptical heart rate detection sensor. The display of the biometricmonitoring device may show whether or not the heart rate has beendetected and/or display the user's heart rate.

Notably, the data from such optical sensors may be representative ofphysiological data and/or environmental data. Indeed, in one embodiment,the optical sensors provide, acquire and/or detect information frommultiple sides of the biometric monitoring device whether or not thesensors are disposed on one or more of the multiple sides. For example,the optical sensors may obtain data related to the ambient lightconditions of the environment.

Where optical sensors are disposed or arranged on the skin-side of thebiometric monitoring device, in operation, a light source in thebiometric monitoring device may emit light upon the skin of the userand, in response, a light detector in the biometric monitoring devicemay sample, acquire, and/or detect corresponding reflected and/oremitted light from the skin (and from inside the body). The one or morelight sources and light detectors may be arranged in an array or patternthat enhances or optimizes the signal-to-noise ratio and/or serves toreduce or minimize power consumption by the light sources and lightdetectors. These optical sensors may sample, acquire and/or detectphysiological data which may then be processed or analyzed (for example,by resident processing circuitry) to obtain data that is representativeof, for example, a user's heart rate, respiration, heart ratevariability, oxygen saturation (SpO₂), blood volume, blood glucose, skinmoisture, and/or skin pigmentation level.

The light source(s) may emit light having one or more wavelengths thatare specific or directed to a type of physiological data to becollected. Similarly, the optical detectors may sample, measure and/ordetect one or more wavelengths that are also specific or directed to atype of physiological data to be collected and/or a physiologicalparameter (of the user) to be assessed or determined. For instance, inone embodiment, a light source emitting light having a wavelength in thegreen spectrum (for example, an LED that emits light having wavelengthscorresponding to the green spectrum) and a photodiode positioned tosample, measure, and/or detect a response or reflection correspondingwith such light may provide data that may be used to determine or detectheart rate. In contrast, a light source emitting light having awavelength in the red spectrum (for example, an LED that emits lighthaving wavelengths corresponding to the red spectrum) and a light sourceemitting light having a wavelength in the infrared spectrum (forexample, an LED that emits light having wavelengths corresponding to theIR spectrum) and photodiode positioned to sample, measure and/or detecta response or reflection of such light may provide data used todetermine or detect SpO₂.

Indeed, in some embodiments, the color or wavelength of the lightemitted by the light source, e.g., an LED (or set of LEDs), may bemodified, adjusted, and/or controlled in accordance with a predeterminedtype of physiological data being acquired or conditions of operation.Here, the wavelength of the light emitted by the light source may beadjusted and/or controlled to optimize and/or enhance the “quality” ofthe physiological data obtained and/or sampled by the detector. Forexample, the color of the light emitted by the LED may be switched frominfrared to green when the user's skin temperature or the ambienttemperature is cool in order to enhance the signal corresponding tocardiac activity. (See, for example, FIG. 11D).

The biometric monitoring device, in some embodiments, may include awindow (for example, a window that is, to casual inspection, opaque) inthe housing to facilitate optical transmission between the opticalsensors and the user. Here, the window may permit light (for example, ofa selected wavelength) to be emitted by, for example, one or more LEDs,onto the skin of the user and a response or reflection of that light topass back through the window to be sampled, measured, and/or detectedby, for example, one or more photodiodes. In one embodiment, thecircuitry related to emitting and receiving light may be disposed in theinterior of the device housing and underneath or behind a plastic orglass layer (for example, painted with infrared ink) or an infrared lensor filter that permits infrared light to pass but not light in the humanvisual spectrum. In this way, the light transmissivity of the window maybe invisible to the human eye.

The biometric monitoring device may employ light pipes or otherlight-transmissive structures to facilitate transmission of light fromthe light sources to the user's body and skin. (See, for example, FIGS.4A through 5). In this regard, in some embodiments, light may bedirected from the light source to the skin of the user through suchlight pipes or other light-transmissive structures. Scattered light fromthe user's body may be directed back to the optical circuitry in thebiometric monitoring device through the same or similar structures.Indeed, the light-transmissive structures may employ a material and/oroptical design to facilitate low light loss (for example, thelight-transmissive structures may include a lens to facilitate lightcollection, and portions of the light-transmissive structures may becoated with or adjacent to reflective materials to promote internalreflection of light within the light-transmissive structures) therebyimproving the signal-to-noise-ratio of the photo detector and/orfacilitating reduced power consumption of the light source(s) and/orlight detectors. In some embodiments, the light pipes or otherlight-transmissive structures may include a material that selectivelytransmits light having one or more specific or predetermined wavelengthswith higher efficiency than others, thereby acting as a bandpass filter.Such a bandpass filter may be tuned to improve the signal of a specificphysiological data type. For example, in one embodiment, anIn-Mold-Labeling or “IML” light-transmissive structure may beimplemented where the light-transmissive structure uses a material withpredetermined or desired optical characteristics to create a specificbandpass characteristic, for example, so as to pass infrared light withgreater efficiency than light of other wavelengths (for example, lighthaving a wavelength in human visible spectrum). In another embodiment, abiometric monitoring device may employ a light-transmissive structurehaving an optically opaque portion (including certain opticalproperties) and an optically-transparent portion (including opticalproperties different from the optically-opaque portion). Such alight-transmissive structure may be provided via a double-shot ortwo-step molding process where optically opaque material and opticallytransparent material are separately injected into a mold. A biometricmonitoring device implementing such a light-transmissive structure mayinclude different light transmissivity properties for differentwavelengths depending on the direction of light travel through thelight-transmissive structure. For example, in one embodiment, theoptically-opaque material may be reflective to a specific wavelengthrange so as to more efficiently transport light from the user's bodyback to the light detector (which may be of a different wavelength(s)relative to the wavelength(s) of the emitted light).

In another embodiment, reflective structures may be placed in the fieldof view of the light emitter(s) and/or light detector(s). For example,the sides of holes that channel light from light emitter(s) to a user'sskin and/or from the user's skin to light detector(s) (or through whichlight-transmissive structures that perform such channeling travel) maybe covered in a reflective material (e.g., chromed) to facilitate lighttransmission. The reflective material may increase the efficiency withwhich the light is transported to the skin from the light source(s) andthen from the skin back into the detector(s). The reflectively-coatedhole may be filled in with an optical epoxy or other transparentmaterial to prevent liquid from entering the device body while stillallowing light to be transmitted with low transmission loss.

In another embodiment that implements light-transmissive structures (forexample, structures created or formed through IML), suchlight-transmissive structures may include a mask consisting of an opaquematerial that limits the aperture of one, some, or all of the lightsource(s) and/or detector(s). In this way, the light-transmissivestructures may selectively “define” a preferential volume of the user'sbody that light is emitted into and/or detected from. Notably, othermask configurations may be employed or implemented in connection withthe concepts described and/or illustrated herein; all such maskingconfigurations to, for example, improve the photoplethysmography signaland which are implemented in connection with the concepts describedand/or illustrated herein are intended to fall within the scope of thepresent disclosure.

In another embodiment, the light emitter(s) and/or detector(s) may beconfigured to transmit light through a hole or series of holes in thedevice exterior. This hole or series of holes may be filled in withlight-transmissive epoxy (e.g. optical epoxy). The epoxy may form alight pipe that allows light to be transmitted from the light emitter(s)to the skin and from the skin back into the light detector(s). Thistechnique also has the advantage that the epoxy may form a watertightseal, preventing water, sweat or other liquid from entering the devicebody though the hole(s) on the device exterior that allow the lightemitter(s) and detector(s) to transmit to, and receive light from, thebiometric monitoring device body exterior. An epoxy with a high thermalconductivity may be used to help prevent the light source(s) (e.g.,LED's) from overheating.

In any of the light-transmissive structures described herein, theexposed surfaces of the optics (light-transmissive structures) or devicebody may include a hard coat paint, hard coat dip, or optical coatings(such as anti-reflection, scratch resistance, anti-fog, and/orwavelength band block (such as ultraviolet light blocking) coatings).Such characteristics or materials may improve the operation, accuracyand/or longevity of the biometric monitoring device.

FIG. 4A illustrates an example of one potential PPG light source andphotodetector geometry. In this embodiment, two light sources are placedon either side of a photodetector. These three devices are located in aprotrusion on the back of a wristband-type biometric monitoring device(the side which faces the skin of the user).

FIGS. 4B and 4C illustrate examples of a PPG sensor having aphotodetector and two LED light sources. These components are placed ina biometric monitoring device that has a protrusion on the back side.Light pipes optically connect the LEDs and photodetector with thesurface of the user's skin. Beneath the skin, the light from the lightsources scatters off of blood in the body, some of which may bescattered or reflected back into the photodetector.

FIG. 5 Illustrates an example of a biometric monitoring device with anoptimized PPG detector that has a protrusion with curved sides so as notto discomfort the user. Additionally, the surface of light pipes thatoptically couple the photodetector and the LEDs to the wearer's skin arecontoured to maximize light flux coupling between the LEDs andphotodetectors and the light pipes. The ends of the light pipes thatface the user's skin are also contoured. This contour may focus ordefocus light to optimize the PPG signal. For example, the contour mayfocus emitted light to a certain depth and location that coincides withan area where blood flow is likely to occur. The vertex of these focimay overlap or be very close together so that the photodetector receivesthe maximum possible amount of scattered light.

In some embodiments, the biometric monitoring device may include aconcave or convex shape, e.g., a lens, on the skin-side of the device,to focus light towards a specific volume at a specific depth in the skinand increase the efficiency of light collected from that point into thephotodetector. (See, for example, FIGS. 4A through 5). Where such abiometric monitoring device also employs light pipes to selectively andcontrollably route light, it may be advantageous to shape the end of thelight pipe with a degree of cylindricity, e.g., the end of the lightpipe may be a be a cylindrical surface (or portion thereof) defined by acylinder axis that is nominally parallel to the skin-side (for example,rather than use an axially-symmetric lens). For example, in awristband-style biometric monitoring device, such a cylindrical lens maybe oriented such that the cylinder axis is nominally parallel to thewearer's forearm, which may have the effect of limiting the amount oflight that enters such a lens from directions parallel to the person'sforearm and increasing the amount of light that enters such a lens fromdirections perpendicular to the person's forearm—since ambient light ismore likely to reach the sensor detection area from directions that arenot occluded by the straps of the biometric monitoring device, i.e.,along the user's forearm axis, than from directions that are occluded bythe straps, i.e., perpendicular to the user's forearm. Such aconfiguration may improve the signal-to-noise-ratio by increasing theefficiency of light transferred from the emitter onto or into the skinof the user while decreasing “stray” light from being detected orcollected by the photodetector. In this way, the signal sampled,measured and/or detected by the photodetector consists less of straylight and more of the user's skin/body response to such emitted light(signal or data that is representative of the response to the emittedlight).

In another embodiment, light-transmissive epoxy may be molded into aconcave or convex shape so as to provide beneficial optical propertiesto sensors as well. For example, during the application of lighttransmissive epoxy, the top of the light-transmissive structure that isformed by the epoxy may be shaped into a concave surface so that lightcouples more effectively into the light-transmissive structure.

In one embodiment, the components of the optical sensor may bepositioned on the skin-side of the device and arranged or positioned toreduce or minimize the distance between (i) the light source(s) and/orthe associated detector(s) and (ii) the skin of the user. See, forexample, FIG. 3A, which provides a cross-sectional view of a sensorprotrusion of an example portable monitoring device. In FIG. 3A, twolight sources (e.g., LEDs) are placed on either side of a photodetectorto enable PPG sensing. A light-blocking material is placed between thelight sources and the photodetector to prevent any light from the lightsources from reaching photodetector without first exiting the body ofthe biometric monitoring device. A flexible transparent layer may beplaced on the lower surface of the sensor protrusion to form a seal.This transparent layer may serve other functions such as preventingliquid from entering the device where the light sources orphotodetectors are placed. This transparent layer may be formed throughin-mold labeling or “IML”. The light sources and photodetector may beplaced on a flexible PCB.

Such a configuration may improve the efficiency of light flux couplingbetween the components of the optical sensor and the user's body. Forexample, in one embodiment, the light source(s) and/or associateddetector(s) may be disposed on a flexible or pliable substrate that mayflex, allowing the skin-side of the biometric monitoring device, whichmay be made from a compliant material, to conform (for example, withoutadditional processing) or be capable of being shaped (or compliant) toconform to the shape of the body part (for example, the user's wrist,arm, ankle, and/or leg) to which the biometric monitoring device iscoupled to or attached during normal operation so that the lightsource(s) and/or associated detector(s) are/is close to the skin of theuser (i.e., with little to no gap between the skin-side of the deviceand the adjacent surface of the skin of the user). See, for example,FIG. 6A. In one embodiment, the light source(s) and/or associateddetector(s) may be disposed on a Flat Flex Cable or “FFC” or flexiblePCB. In this embodiment, the flexible or pliable substrate (for example,an FFC or flexible PCB) may connect to a second substrate (for example,PCB) within the device having other components disposed thereon (forexample, the data processing circuitry). Optical components of differingheights may be mounted to different “fingers” of flexible substrate andpressed or secured to the housing surface such that the opticalcomponents are flush to the housing surface. In one embodiment, thesecond substrate may be a relatively inflexible or non-pliablesubstrate, fixed within the device, having other circuitry andcomponents (passive and/or active) disposed thereon.

FIG. 3B depicts a cross-sectional view of a sensor protrusion of anexample portable monitoring device; this protrusion is similar to thatpresented in FIG. 3A with the exception that the light sources andphotodetector are placed on a flat and/or rigid PCB.

FIG. 3C provides another cross-sectional view of an example PPG sensorimplementation. Of note in this PPG sensor is the lack of a protrusion.Additionally, a liquid gasket and/or a pressure sensitive adhesive areused to prevent liquid from entering the biometric monitoring devicebody.

Some embodiments of biometric monitoring devices may be adapted to beworn or carried on the body of a user. In some embodiments including theoptical heart rate monitor, the device may be a wrist-worn orarm-mounted accessory such as a watch or bracelet. (See, for example,FIGS. 2A through 7). In one embodiment, optical elements of the opticalheart rate monitor may be located on the interior or skin-side of thebiometric monitoring device, for example, facing the top of the wrist(i.e., the optical heart rate monitor may be adjacent to and facing thewrist) when the biometric monitoring device is worn on the wrist. (See,for example, FIGS. 2A through 3C).

In another embodiment, the optical heart rate monitor may be located onone or more external or environmental side surfaces of the biometricmonitoring device. (See, for example, FIGS. 6B and 7). In suchembodiments, the user may touch an optical window (behind which opticalelements of the optical heart rate monitor are located) with a finger onthe opposing hand to initiate a heart rate measurement (and/or othermetrics related to heart rate such as heart rate variability) and/orcollect data which may be used to determine the user's heart rate(and/or other metrics related to heart rate). (See, for example, FIG.6B). In one embodiment, the biometric monitoring device may trigger orinitiate the measurement(s) by detecting a (sudden) drop in incidentlight on the photodiode—for example, when the user's finger is placedover the optical window. In addition thereto, or in lieu thereof, aheart rate measurement (or other such metric) may be trigged by anIR-based proximity detector and/or capacitive touch/proximity detector(which may be separate from other detectors). Such IR-based proximitydetector and/or capacitive touch/proximity detector may be disposed inor on and/or functionally, electrically and/or physically coupled to theoptical window to detect or determine the presence of, for example, theuser's finger.

In yet another embodiment, the biometric monitoring device may include abutton that, when depressed, triggers or initiates heart ratemeasurement (and/or other metrics related to heart rate). The button maybe disposed in close proximity to the optical window to facilitate theuser pressing the button while the finger is disposed on the opticalwindow. (See, for example, FIG. 7). In one embodiment, the opticalwindow may be embedded in a push button. Thus, when the user presses thebutton, it may trigger a measurement of the finger that depresses thebutton. Indeed, the button may be given a shape and/or resistance topressing that enhances or optimizes a pressure profile of the buttonagainst the finger to provide a high signal-to-noise-ratio duringmeasurement or data acquisition. In other embodiments (not illustrated),the biometric monitoring device may take the form of a clip, a smoothobject, a pendant, an anklet, a belt, etc. that is adapted to be worn onthe body, clipped or mounted to an article of clothing, deposited inclothing (e.g., in a pocket), or deposited in an accessory (e.g.,handbag).

In one specific embodiment, the biometric monitoring device may includea protrusion on the skin- or interior side of the device. (See, FIGS. 2Athrough 6A). When coupled to the user, the protrusion may engage theskin with more force than the surrounding device body. In thisembodiment, an optical window or light transmissive structure (both ofwhich are discussed in detail above) may form or be incorporated in aportion of the protrusion. The light emitter(s) and/or detector(s) ofthe optical sensor may be disposed or arranged in the protrusion nearthe window or light transmissive structure. (See, for example, FIGS. 2Band 6A). As such, when attached to the user's body, the window portionof the protrusion of the biometric monitoring device may engage theuser's skin with more force than the surrounding device body—therebyproviding a more secure physical coupling between the user's skin andthe optical window. That is, the protrusion may cause sustained contactbetween the biometric monitoring device and the user's skin that mayreduce the amount of stray light measured by the photodetector, decreaserelative motion between the biometric monitoring device and the user,and/or provide improved local pressure to the user's skin; all of whichmay increase the quality of the cardiac signal of interest. Notably, theprotrusion may contain other sensors that benefit from close proximityand/or secure contact to the user's skin. These may be included inaddition to or in lieu of a heart rate sensor and include sensors suchas a skin temperature sensor (e.g., noncontact thermopile that utilizesthe optical window or thermistor joined with thermal epoxy to the outersurface of the protrusion), pulse oximeter, blood pressure sensor, EMG,or galvanic skin response (GSR) sensor.

In addition thereto, or in lieu thereof, a portion of the skin-side ofthe biometric monitoring device may include a friction enhancingmechanism or material. For example, the skin-side of the biometricmonitoring device may include a plurality of raised or depressed regionsor portions (for example, small bumps, ridges, grooves, and/or divots).Moreover, a friction enhancing material (for example, a gel-likematerial such as silicone or other elastomeric material) may be disposedon the skin-side. Indeed, a device back made out of gel may also providefriction while also improving user comfort and preventing stray lightfrom entering. As noted above, a friction-enhancing mechanism ormaterial may be used alone or in conjunction with the biometricmonitoring device having a protrusion as described herein. In thisregard, the biometric monitoring device may include a plurality ofraised or depressed regions or portions (for example, small bumps,ridges, grooves, and/or divots) in or on the protrusion portion of thedevice. Indeed, such raised or depressed regions or portions may beincorporated/embedded into or on a window portion of the protrusion. Inaddition thereto, or in lieu thereof, the protrusion portion may consistof or be coated with a friction enhancing material (for example, agel-like material such as silicone). Notably, the use of a protrusionand/or friction may improve measurement accuracy of data acquisitioncorresponding to certain parameters (e.g., heart rate, heart ratevariability, galvanic skin response, skin temperature, skin coloration,heat flux, blood pressure, blood glucose, etc.) by reducing motion ofthe biometric monitoring device (and thus of the sensor) relative to theuser's skin during operation, especially while the user is in motion.

Some or all of the interior or skin-side housing of the biometricmonitoring device may also consist of a metal material (for example,steel, stainless steel, aluminum, magnesium, or titanium). Such aconfiguration may provide a structural rigidity. (See, for example, FIG.2B). In such an embodiment, the device body may be designed to behypoallergenic through the use of a hypoallergenic “nickel-free”stainless steel. Notably, it may be advantageous to employ (at least incertain locations) a type of metal that is at least somewhat ferrous(for example, a grade of stainless steel that is ferrous). In suchembodiments, the biometric monitoring device (where it includes arechargeable energy source (for example, rechargeable battery)) mayinterconnect with a charger via a connector that secures itself to thebiometric monitoring device using magnets that couple to the ferrousmaterial. In addition, biometric monitoring device may also engage adock or dock station, using such magnetic properties, to facilitate datatransfer. Moreover, such a housing may provide enhanced electromagneticshielding that would enhance the integrity and reliability of theoptical heart rate sensor and the heart rate data acquisitionprocess/operation. Furthermore, a skin temperature sensor may bephysically and thermally coupled, for example, with thermal epoxy, tothe metal body to sense the temperature of the user. In embodimentsincluding a protrusion, the sensor may be positioned near or in theprotrusion to provide secure contact and localized thermal coupling tothe user's skin.

In a preferred embodiment, one or more components of the optical sensor(which may, in one embodiment, be located in a protrusion, and/or inanother embodiment, may be disposed or placed flush to the surface ofthe biometric monitoring device) are attached, fixed, included, and/orsecured to the biometric monitoring device via a liquid-tight seal(i.e., a method/mechanism that prevents liquid ingress into the body ofthe biometric monitoring device). For example, in one embodiment, adevice back made out of a metal such as, but not limited to, stainlesssteel, aluminum, magnesium, or titanium, or from a rigid plastic mayprovide a structure that is stiff enough to maintain the structuralintegrity of the device while accommodating a watertight seal for thesensor package. (See, for example, FIGS. 2B through 3C).

In a preferred embodiment, a package or module of the optical sensor maybe connected to the device with a pressure-sensitive adhesive and aliquid gasket. See, for example, FIG. 3C, which provides anothercross-sectional view of a PPG sensor implementation. Of note in this PPGsensor is the lack of a protrusion. Additionally, a liquid gasket and/ora pressure sensitive adhesive are used to prevent liquid from enteringthe device body. Screws, rivets or the like may also be used, forexample, if a stronger or more durable connection is required betweenthe optical sensor package/module and the device body. Notably, thepresent embodiments may also use watertight glues, hydrophobic membranessuch as Gore-Tex, o-rings, sealant, grease, or epoxy to secure or attachthe optical sensor package/module to the biometric monitoring devicebody.

As discussed above, the biometric monitoring device may include amaterial disposed on the skin- or interior side that includes highreflectivity characteristics—for example, polished stainless steel,reflective paint, and polished plastic. In this way, light scattered offthe skin-side of the device may be reflected back into the skin in orderto, for example, improve the signal-to-noise-ratio of an optical heartrate sensor. Indeed, this effectively increases the input light signalas compared with a device body back that is non-reflective (or lessreflective). Notably, in one embodiment, the color of the skin orinterior side of the biometric monitoring device may be selected toprovide certain optical characteristics (for example, reflect certain orpredetermined wavelengths of light), in order to improve the signal withrespect to certain physiological data types. For example, where theskin- or interior side of the biometric monitoring device is green, themeasurements of the heart rate may be enhanced due to the preferentialemission of a wavelength of the light corresponding to the greenspectrum. Where the skin- or interior side of the biometric monitoringdevice is red, the measurements of the SpO₂ may be enhanced due to thepreferential emission of a wavelength of the light corresponding to thered spectrum. In one embodiment, the color of the skin- or interior sideof the biometric monitoring device may be modified, adjusted and/orcontrolled in accordance with a predetermined type of physiological databeing acquired.

FIG. 11A depicts an example schematic block diagram of an optical heartrate sensor where light is emitted from a light source toward the user'sskin and the reflection of such light from the skin/internal body of theuser is sensed by a light detector, the signal from which issubsequently digitized by an analog to digital converter (ADC). Theintensity of the light source may be modified (e.g., through a lightsource intensity control module) to maintain a desirable reflectedsignal intensity. For example, the light source intensity may be reducedto avoid saturation of the output signal from the light detector. Asanother example, the light source intensity may be increased to maintainthe output signal from the light detector within a desired range ofoutput values. Notably, active control of the system may be achievedthrough linear or nonlinear control methods such asproportional-integral-derivative (PID) control, fixed step control,predictive control, neural networks, hysteresis, and the like, and mayalso employ information derived from other sensors in the device such asmotion, galvanic skin response, etc. FIG. 11A is provided forillustration and does not limit the implementation of such a system to,for instance, an ADC integrated within a MCU, or the use of a MCU forthat matter. Other possible implementations include the use of one ormore internal or external ADCs, FPGAs, ASICs, etc.

In another embodiment, system with an optical heart rate sensor mayincorporate the use of a sample-and-hold circuit (or equivalent) tomaintain the output of the light detector while the light source isturned off or attenuated to save power. In embodiments where relativechanges in the light detector output are of primary importance (e.g.,heart rate measurement), the sample-and-hold circuit may not have tomaintain an accurate copy of the output of the light detector. In suchcases, the sample-and-hold may be reduced to, for example, a diode(e.g., Schottky diode) and capacitor. The output of the sample-and-holdcircuit may be presented to an analog signal conditioning circuit (e.g.,a Sallen-Key bandpass filter, level shifter, and/or gain circuit) tocondition and amplify the signal within frequency bands of interest(e.g., 0.1 Hz to 10 Hz for cardiac or respiratory function), which maythen be digitized by the ADC. See, for example, FIG. 11B.

In operation, circuit topologies such as those already described herein(e.g. a sample-and-hold circuit) remove the DC and low frequencycomponents of the signal and help resolve the AC component related toheart rate and/or respiration. The embodiment may also include theanalog signal conditioning circuitry for variable gain settings that canbe controlled to provide a suitable signal (e.g., not saturated). Theperformance characteristics (e.g., slew rate and/or gain bandwidthproduct) and power consumption of the light source, light detector,and/or sample-and-hold may be significantly higher than the analogsignal conditioning circuit to enable fast duty cycling of the lightsource. In some embodiments, the power provided to the light source andlight detector may be controlled separately from the power provided tothe analog signal conditioning circuit to provide additional powersavings. Alternatively or additionally, the circuitry can usefunctionality such as an enable, disable and/or shutdown to achievepower savings. In another embodiment, the output of the light detectorand/or sample-and-hold circuit may be sampled by an ADC in addition toor in lieu of the analog signal conditioning circuit to control thelight intensity of the light source or to measure the physiologicparameters of interest when, for example, the analog signal conditioningcircuit is not yet stable after a change to the light intensity setting.Notably, because the physiologic signal of interest is typically smallrelative to the inherent resolution of the ADC, in some embodiments, thereference voltages and/or gain of the ADC may be adjusted to enhancesignal quality and/or the ADC may be oversampled. In yet anotherembodiment, the device may digitize the output of only thesample-and-hold circuit by, for example, oversampling, adjusting thereference voltages and/or gain of the ADC, or using a high resolutionADC. See, for example, FIG. 11C.

PPG DC Offset Removal Techniques

In another embodiment, the sensor device may incorporate a differentialamplifier to amplify the relative changes in the output of the lightdetector. See, for example, FIG. 11F. In some embodiments, a digitalaverage or digital low-pass filtered signal may be subtracted from theoutput of the light detector. This modified signal may then be amplifiedbefore it is digitized by the ADC. In another embodiment, an analogaverage or analog low-pass filtered signal may be subtracted from theoutput of the light detector through, for example, the use of asample-and-hold circuit and analog signal conditioning circuitry. Thepower provided to the light source, light detector, and differentialamplifier may be controlled separately from the power provided to theanalog signal conditioning circuit to improve power savings.

In another embodiment, a signal (voltage or current, depending on thespecific sensor implementation) may be subtracted from the raw PPGsignal to remove any bias in the raw PPG signal and therefore increasethe gain or amplification of the PPG signal that contains heart rate (orother circulatory parameters such as heart rate variability)information. This signal may be set to a default value in the factory,to a value based on the user's specific skin reflectivity, absorption,and/or color, and/or may change depending on feedback from an ambientlight sensor, or depending on analytics of the PPG signal itself. Forexample, if the PPG signal is determined to have a large DC offset, aconstant voltage may be subtracted from the PPG signal to remove the DCoffset and enable a larger gain, therefore improving the PPG signalquality. The DC offset in this example may result from ambient light(for example from the sun or from indoor lighting) reaching thephotodetector from or reflected light from the PPG light source.

In another embodiment, a differential amplifier may be used to measurethe difference between current and previous samples rather than themagnitude of each signal. Since the magnitude of each sample istypically much greater than the difference between each sample, a largergain can be applied to each measurement, therefore improving the PPGsignal quality. The signal may then be integrated to obtain the originaltime domain signal.

In another embodiment, the light detector module may incorporate atransimpedance amplifier stage with variable gain. Such a configurationmay avoid or minimize saturation from bright ambient light and/or brightemitted light from the light source. For example, the gain of thetransimpedance amplifier may be automatically reduced with a variableresistor and/or multiplexed set of resistors in the negative feedbackpath of the transimpedance amplifier. In some embodiments, the devicemay incorporate little to no optical shielding from ambient light byamplitude-modulating the intensity of the light source and thendemodulating the output of the light detector (e.g., synchronousdetection). See, for instance, FIG. 11E. In other aspects, if theambient light is of sufficient brightness to obtain a heart rate signal,the light source may be reduced in brightness and/or turned offcompletely.

In yet another embodiment, the aforementioned processing techniques maybe used in combination to optically measure physiological parameters ofthe user. See, for example, FIG. 11G. This topology may allow the systemto operate in a low power measurement state and circuit topology whenapplicable and adapt to a higher power measurement state and circuittopology as necessary. For instance, the system may measure thephysiologic parameter (e.g., heart rate) of interest using analogsignal-conditioning circuitry while the user is immobile or sedentary toreduce power consumption, but switch to oversampled sampling of thelight detector output directly while the user is active.

In embodiments where the biometric monitoring device includes a heartrate monitor, processing of the signal to obtain heart rate measurementsmay include filtering and/or signal conditioning such as band-passfiltering (e.g., Butterworth filter). To counteract large transientsthat may occur in the signal and/or to improve convergence of saidfiltering, nonlinear approaches may be employed such as neural networksor slew rate limiting. Data from the sensors on the device such asmotion, galvanic skin response, skin temperature, etc., may be used toadjust the signal conditioning methods employed. Under certain operatingconditions, the heart rate of the user may be measured by counting thenumber of signal peaks within a time window or by utilizing thefundamental frequency or second harmonic of the signal (e.g., through afast Fourier transform (FFT)). In other cases, such as heart rate dataacquired while the user is in motion, FFTs may be performed on thesignal and spectral peaks extracted, which may then be subsequentlyprocessed by a multiple-target tracker which starts, continues, merges,and deletes tracks of the spectra. In some embodiments, a similar set ofoperations may be performed on the motion signal and the output may beused to do activity discrimination (e.g., sedentary, walking, running,sleeping, lying down, sitting, biking, typing, elliptical, weighttraining) which is used to assist the multiple-target tracker. Forinstance, it may be determined that the user was stationary and hasbegun to move. This information may be used to preferentially bias thetrack continuation toward increasing frequencies. Similarly, theactivity discriminator may determine that the user has stopped runningor is running slower and this information may be used to preferentiallybias the track continuation toward decreasing frequencies. Tracking maybe achieved with single-scan or multi-scan, multiple-target trackertopologies such as joint probabilistic data association trackers,multiple-hypothesis tracking, nearest neighbor, etc. Estimation andprediction in the tracker may be done through Kalman filters, splineregression, particle filters, interacting multiple model filters, etc. Atrack selector module may use the output tracks from themultiple-spectra tracker and estimate the user's heart rate. Theestimate may be taken as the maximum likelihood track, a weight sum ofthe tracks against their probabilities of being the heart rate, etc. Theactivity discriminator may furthermore influence the selection and/orfusion to get the heart rate estimate. For instance, if the user issleeping, sitting, lying down, or sedentary, a prior probability may beskewed toward heart rates in the 40-80 bpm range; whereas if the user isrunning, jogging, or doing other vigorous exercise, a prior probabilitymay be skewed toward elevated heart rates in the 90-180 bpm range. Theinfluence of the activity discriminator may be based on the speed of theuser. The estimate may be shifted toward (or wholly obtained by) thefundamental frequency of the signal when the user is not moving. Thetrack that corresponds to the user's heart rate may be selected based oncriteria that are indicative of changes in activity; for instance, ifthe user begins to walk from being stationary, the track thatillustrates a shift toward higher frequency may be preferentiallychosen.

The acquisition of a good heart rate signal may be indicated to the userthrough a display on the biometric monitoring device or another devicein wired or wireless communication with the biometric monitoring device(e.g., a Bluetooth Low Energy-equipped mobile phone). In someembodiments, the biometric monitoring device may include asignal-strength indicator that is represented by the pulsing of an LEDviewable by the user. The pulsing may be timed or correlated to becoincident with the user's heartbeat. The intensity, pulsing rate and/orcolor of the LED may be modified or adjusted to suggest signal strength.For example, a brighter LED intensity may represent a stronger signal orin an RGB LED configuration, a green colored LED may represent astronger signal.

In some embodiments, the strength of the heart rate signal may bedetermined by the energy (e.g., squared sum) of the signal in afrequency band of, for instance, 0.5 Hz to 4 Hz. In other embodiments,the biometric monitoring device may have a strain gauge, pressuresensor, force sensor, or other contact-indicating sensor that may beincorporated or constructed into the housing and/or in the band (inthose embodiments where the biometric monitoring device is attached toor mounted with a band like a watch, bracelet, and/or armband—which maythen be secured to the user). A signal quality metric (e.g. heart ratesignal quality) may be calculated based on data from these contactsensors either alone or in combination with data from the heart ratesignal.

In another embodiment, the biometric monitoring device may monitor heartrate optically through an array of photodetectors such as a grid ofphotodiodes or a CCD camera. Motion of the optical device with respectto the skin may be tracked through feature-tracking of the skin and/oradaptive motion correction using an accelerometer and gyroscope. Thedetector array may be in contact with the skin or offset at a smalldistance away from the skin. The detector array and its associatedoptics may be actively controlled (e.g., with a motor) to maintain astabilized image of the target and acquire a heart rate signal. Thisoptomechanical stabilization may be achieved using information frommotion sensors (e.g., a gyroscope) or image features. In one embodiment,the biometric monitoring device may implement relative motioncancellation using a coherent or incoherent light source to illuminatethe skin and a photodetector array with each photodetector associatedwith comparators for comparing the intensity between neighboringdetectors—obtaining a so-called speckle pattern which may be trackedusing a variety of image tracking techniques such as optical flow,template matching, edge tracking, etc. In this embodiment, the lightsource used for motion tracking may be different than the light sourceused in the optical heart rate monitor.

In another embodiment, the biometric monitoring device may consist of aplurality of photodetectors and photoemitters distributed along asurface of the device that touches the user's skin (i.e., the skin-sideof the biometric monitoring device). (See, for example, FIGS. 2A through6A). In the example of a bracelet, for instance, there may be aplurality of photodetectors and photoemitters placed at various sitesalong the circumference of the interior of the band. (See, for example,FIG. 6A). A heart rate signal-quality metric associated with each sitemay be calculated to determine the best or set of best sites forestimating the user's heart rate. Subsequently, some of the sites may bedisabled or turned off to, for example, reduce power consumption. Thedevice may periodically check the heart rate signal quality at some orall of the sites to enhance, monitor and/or optimize signal and/or powerefficiency.

In another embodiment, a biometric monitoring device may include a heartrate monitoring system including a plurality of sensors such as optical,acoustic, pressure, electrical (e.g., ECG or EKG), and motion and fusethe information from two or more of these sensors to provide an estimateof heart rate and/or mitigate noise induced from motion.

In addition to heart rate monitoring (or other biometric monitoring), orin lieu thereof, the biometric monitoring device, in some embodiments,may include optical sensors to track or detect time and duration ofultraviolet light exposure, total outdoor light exposure, the type oflight source and duration and intensity of that light source(fluorescent light exposure, incandescent bulb light exposure, halogen,etc.), exposure to television (based on light type and flicker rate),whether the user is indoors or outdoors, time of day and location basedon light conditions. In one embodiment, the ultraviolet detection sensormay consist of a reverse biased LED emitter driven as a light detector.The photocurrent produced by this detector may be characterized by, forinstance, measuring the time it takes for the LED's capacitance (oralternately a parallel capacitor) to discharge.

All of the optical sensors discussed herein may be used in conjunctionwith other sensors to improve detection of the data described above orbe used to augment detection of other types of physiological orenvironmental data.

Where the biometric monitoring device includes an audio or passiveacoustic sensor, the device may contain one or more passive acousticsensors that detect sound and pressure and that can include, but are notlimited to, microphones, piezo films, etc. The acoustic sensors may bedisposed on one or more sides of the device, including the side thattouches or faces the skin (skin-side) and the sides that face theenvironment (environmental sides).

Skin-side acoustic or audio sensors may detect any type of soundtransmitted through the body and such sensors may be arranged in anarray or pattern that optimizes both the signal-to-noise-ratio and powerconsumption of such sensors. These sensors may detect respiration (e.g.,by listening to the lung), respiratory sounds (e.g., breathing, snoring)and problems (e.g., sleep apnea, etc.), heart rate (listening to theheart beat), user's voice (via sound transmitted from the vocal cordsthroughout the body).

The biometric monitoring devices of the present disclosure may alsoinclude galvanic skin-response (GSR) circuitry to measure the responseof the user's skin to emotional and physical stimuli or physiologicalchanges (e.g., the transition of sleep stage). In some embodiments, thebiometric monitoring device may be a wrist- or arm-mounted deviceincorporating a band made of conductive rubber or fabric so that thegalvanic skin response electrodes may be hidden in the band. Because thegalvanic skin response circuitry may be subjected to changingtemperatures and environmental conditions, it may also include circuitryto enable automatic calibration, such as two or more switchablereference resistors in parallel or in series with the humanskin/electrode path that allows real-time measurement of known resistorsto characterize the response of the galvanic skin response circuit. Thereference resistors may be switched into and out of the measurement pathsuch that they are measured independently and/or simultaneously with theresistance of the human skin.

Circuits for Performing PPG

PPG circuitry may be optimized to obtain the best quality signalregardless of a variety of environmental conditions including, but notlimited to, motion, ambient light, and skin color. The followingcircuits and techniques may be used to perform such optimization (seeFIGS. 16A through 16J);

-   -   a sample-and-hold circuit and differential/instrumentation        amplifier which may be used in PPG sensing. The output signal is        an amplified difference between current and previous sample,        referenced to a given voltage.    -   controlled current source to offset “bias” current prior to        transimpedance amplifier. This allows greater gain to be applied        at transimpedance amplifier stage.    -   a sample-and-hold circuit for current feedback applied to        photodiode (prior to transimpedance amplifier). This can be used        for ambient light removal, or “bias” current removal, or as a        pseudo differential amplifier (may require dual rails).    -   a differential/instrumentation amplifier with ambient light        cancellation.    -   a photodiode offset current generated dynamically by a DAC.    -   a photodiode offset current generated dynamically by controlled        voltage source.    -   ambient light removal using a “switched capacitor” method.    -   photodiode offset current generated by a constant current source        (also can be done with a constant voltage source and a        resistor).    -   ambient light removal and differencing between consecutive        samples.    -   ambient light removal and differencing between consecutive        samples.

FIG. 16A illustrates an example schematic of a sample-and-hold circuitand differential/instrumentation amplifier which may be used in PPGsensing. The output signal in such a circuit may be an amplifieddifference between a current sample and a previous sample, referenced toa given voltage.

FIG. 16B illustrates an example schematic of a circuit for a PPG sensorusing a controlled current source to offset “bias” current prior to atransimpedance amplifier. This allows greater gain to be applied at thetransimpedance amplifier stage.

FIG. 16C illustrates an example schematic of a circuit for a PPG sensorusing a sample-and-hold circuit for current feedback applied tophotodiode (prior to a transimpedance amplifier). This circuit may beused for ambient light removal, or “bias” current removal, or as apseudo-differential amplifier.

FIG. 16D illustrates an example schematic of a circuit for a PPG sensorusing a differential/instrumentation amplifier with ambient lightcancellation functionality.

FIG. 16E illustrates an example schematic of a circuit for a PPG sensorusing a photodiode offset current generated dynamically by a DAC.

FIG. 16F illustrates an example schematic of a circuit for a PPG sensorusing a photodiode offset current generated dynamically by a controlledvoltage source.

FIG. 16G illustrates an example schematic of a circuit for a PPG sensorincluding ambient light removal functionality using a “switchedcapacitor” method.

FIG. 16H illustrates an example schematic of a circuit for a PPG sensorthat uses a photodiode offset current generated by a constant currentsource (this may also be done using a constant voltage source and aresistor).

FIG. 16I illustrates an example schematic of a circuit for a PPG sensorthat includes ambient light removal functionality and differencingbetween consecutive samples.

FIG. 16J illustrates an example schematic of a circuit for ambient lightremoval and differencing between consecutive samples.

Various circuits and concepts related to heart rate measurement using aPPG sensor are discussed in more detail in U.S. Provisional PatentApplication No. 61/946,439, filed Feb. 28, 2014, which was previouslyincorporated herein by reference in the “Cross-Reference to RelatedApplications” section and which is again hereby incorporated byreference with respect to content directed at heart rate measurementswith a PPG sensor and at circuits, methods, and systems for performingsuch measurements, e.g., to compensate for sensor saturation, ambientlight, and skin tone.

Biometric Feedback

Some embodiments of biometric monitoring devices may provide feedback tothe user based on one or more biometric signals. In one embodiment, aPPG signal may be presented to the user as a real-time or near-real-timewaveform on a display of the biometric monitoring device (or on adisplay of a secondary device in communication with the biometricmonitoring device). This waveform may provide similar feedback to thewaveform displayed on an ECG or EKG machine. In addition to providingthe user with an indication of the PPG signal which may be used toestimate various heart metrics (e.g., heart rate), the waveform may alsoprovide feedback that may enable the user to optimize the position andpressure with which they are wearing the biometric monitoring device.For example, the user may see that the waveform has a low amplitude. Inresponse to this, the user may try moving the position of the biometricmonitoring device to a different location which gives a higher amplitudesignal. In some implementations, the biometric monitoring device may,based on such indications, provide instructions to the user to move oradjust the fit of the biometric monitoring device so as to improve thesignal quality.

In another embodiment, feedback about the quality of the PPG signal maybe provided to the user through a method other than displaying thewaveform. The biometric monitoring device may emit an auditory alarm(e.g. a beep) if the signal quality (e.g. signal to noise ratio) exceedsa certain threshold. The biometric monitoring device may provide avisual cue (through the use of a display for example) to the user toeither change the position of the sensor and/or increase the pressurewith which the device is being worn (for example by tightening a wriststrap in the case that the device is worn on the wrist).

Biometric feedback may be provided for sensors other than PPG sensors.For example, if the device uses ECG, EMG, or is connected to a devicewhich performs either of these, it may provide feedback to the userregarding the waveform from those sensors. If the signal-to-noise-ratioof these sensors is low, or the signal quality is otherwise compromised,the user may be instructed on how they can improve the signal. Forexample, if the heart rate cannot be detected from the ECG sensor, thedevice may provide a visual message to the user instructing them to wetor moisten the ECG electrodes to improve the signal.

Environmental Sensors

Some embodiments of biometric monitoring devices of the presentdisclosure may use one, some or all of the following environmentalsensors to, for example, acquire the environmental data, includingenvironmental data outlined in the table below. Such biometricmonitoring devices are not limited to the number or types of sensorsspecified below but may employ other sensors that acquire environmentaldata outlined in the table below. All combinations and permutations ofenvironmental sensors and/or environmental data are intended to fallwithin the scope of the present disclosure. Additionally, the device mayderive environmental data from the corresponding sensor output data, butis not limited to the types of environmental data that it could derivefrom said sensor.

Notably, embodiments of biometric monitoring devices of the presentdisclosure may use one or more, or all of the environmental sensorsdescribed herein and one or more, or all of the physiological sensorsdescribed herein. Indeed, biometric monitoring device of the presentdisclosure may acquire any or all of the environmental data andphysiological data described herein using any sensor now known or laterdeveloped—all of which are intended to fall within the scope of thepresent disclosure.

Environmental Sensors Environmental data acquired Motion DetectorLocation Potential Embodiments: Inertial, Gyroscopic or Accelerometer-based Sensors GPS Pressure/Altimeter sensor Elevation Ambient TempTemperature Light Sensor Indoor vs outdoor Watching TV (spectrum/flicker rate detection) Optical data transfer-initiation, QR codes, etc.Ultraviolet light exposure Audio Indoor vs. Outdoor Compass Locationand/or orientation Potential Embodiments: 3 Axis Compass

In one embodiment, the biometric monitoring device may include analtimeter sensor, for example, disposed or located in the interior ofthe device housing. (See, for example, FIGS. 12B and 12C; FIG. 12Cillustrates an example of a portable biometric monitoring device havingphysiological sensors, environmental sensors, and location sensorsconnected to a processor). In such a case, the device housing may have avent that allows the interior of the device to measure, detect, sampleand/or experience any changes in exterior pressure. In one embodiment,the vent may prevent water from entering the device while facilitatingmeasuring, detecting and/or sampling changes in pressure via thealtimeter sensor. For example, an exterior surface of the biometricmonitoring device may include a vent type configuration or architecture(for example, a Gore™ vent) that allows ambient air to move in and outof the housing of the device (which allows the altimeter sensor tomeasure, detect and/or sample changes in pressure), but reduces,prevents, and/or minimizes water and other liquids from flowing into thehousing of the device.

The altimeter sensor, in one embodiment, may be filled with gel thatallows the sensor to experience pressure changes outside of the gel. Thegel may act as a relatively impervious, incompressible, yet flexible,membrane that transmits external pressure variations to the altimeterwhile physically separating the altimeter (and other internalcomponents) from the outside environment. The use of a gel-filledaltimeter may give the device a higher level of environmental protectionwith or without the use of an environmentally sealed vent. The devicemay have a higher survivability rate with a gel-filled altimeter inlocations including, but not limited to, locations that have highhumidity, clothes washers, dish washers, clothes dryers, a steam room orsauna, a shower, a pool, a bath, and any location where the device maybe exposed to moisture, exposed to liquid, or submerged in liquid.

Sensors Integration/Signal Processing

Some embodiments of the biometric monitoring devices of the presentdisclosure may use data from two or more sensors to calculate thecorresponding physiological or environmental data as seen in the tablebelow (for example, data from two or more sensors may be used incombination to determine metrics such as those listed below). Thebiometric monitoring device may include, but is not limited to, thenumber, types, or combinations of sensors specified below. Additionally,such biometric monitoring devices may derive the included data from thecorresponding sensor combinations, but are not limited to the number ortypes of data that may be calculated from the corresponding sensorcombinations.

Sensor Data derived from signal Integrations processing of multiplesensors Skin Temp and Ambient Temp Heat Flux Heart Rate and MotionElevation gain Motion detector and other user's motion Users in theproximity detector (linked by wireless communication path) Motion, anyheart rate sensor, galvanic Sit/ Standing detection skin response Anyheart rate, heart rate variability Sleep Phase detection sensor,respiration, motion Sleep Apnea detection Any heart rate sensor and/orwetness Resting Heart rate sensor, and/or motion detector Active HeartRate Heart rate while asleep Heart rate while sedentary Any heart ratedetector Early detection of heart problems: Cardiac Arrhythmia CardiacArrest Multiple heart rate detectors Pulse transit time Audio and/orstrain gauge Typing detection GPS and photoplethysmography (PPG)Location-stress correlation: determination of stressful regionsdetermination of low stress regions Activity-specific heart rate restingheart rate active heart rate Automatic activity classification andactivity heart rate determination Heart rate, galvanic skin response,User fatigue, for example accelerometer and respiration while exercising

In some embodiments, the biometric monitoring device may also include anear-field communication (NFC) receiver/transmitter to detect proximityto another device, such as a mobile phone. When the biometric monitoringdevice is brought into close or detectable proximity to the seconddevice, it may trigger the start of new functionality on the seconddevice (e.g., the launching of an “app” on the mobile phone and radiosyncing of physiological data from the device to the second device).(See, for example, FIG. 10). Indeed, the biometric monitoring device ofthe present disclosure may implement any of the circuitry and techniquesdescribed and/or illustrated in U.S. Provisional Patent Application61/606,559, filed Mar. 5, 2012, “Near Field Communication System, andMethod of Operating Same”, inventor: James Park (the contents of whichare incorporated herein by reference for such purpose).

FIG. 10 illustrates an example of a portable biometric monitoring devicethat has a bicycle application on it that may display bicycle speedand/or pedaling cadence, among other metrics. The app may be activatedwhenever the biometric monitoring device comes into proximity of apassive or active NFC tag. This NFC tag may be attached to the user'shandlebars.

In another embodiment, the biometric monitoring device may include alocation sensor (for example, GPS circuitry) and heart rate sensor (forexample, photoplethysmography circuitry) to generate GPS- orlocation-related data and heart rate-related data, respectively. (See,for example, FIGS. 12B and 12C). The biometric monitoring device maythen fuse, process and/or combine data from these twosensors/circuitries to, for example, determine, correlate, and/or “map”geographical regions according to physiological data (for example, heartrate, stress, activity level, quantity of sleep and/or caloric intake).In this way, the biometric monitoring device may identify geographicalregions that increase or decrease a measurable user metric including,but not limited to, heart rate, stress, activity, level, quantity ofsleep and/or caloric intake.

In addition thereto, or in lieu thereof, some embodiments of biometricmonitoring devices may employ GPS-related data andphotoplethysmography-related data (notably, each of which may beconsidered data streams) to determine or correlate the user's heart rateaccording to activity levels—for example, as determined by the user'sacceleration, speed, location and/or distance traveled (as measured bythe GPS and/or determined from GPS-related data). (See, for example,FIGS. 12B and 12C). Here, in one embodiment, heart rate as a function ofspeed may be “plotted” for the user, or the data may be broken down intodifferent levels including, but not limited to, sleeping, resting,sedentary, moderately active, active, and highly active.

Indeed, some embodiments of biometric monitoring devices may alsocorrelate GPS-related data to a database of predetermined geographiclocations that have activities associated with them for a set ofpredetermined conditions. For example, activity determination andcorresponding physiological classification (for example, heart rateclassification) may include correlating a user's GPS coordinates thatcorrespond to location(s) of exercise equipment, health club and/or gymand physiological data. Under these circumstances, a user's heart rateduring, for example a gym workout, may be automatically measured anddisplayed. Notably, many physiological classifications may be based onGPS-related data including location, acceleration, altitude, distanceand/or velocity. Such a database including geographic data andphysiological data may be compiled, developed and/or stored on thebiometric monitoring device and/or external computing device. Indeed, inone embodiment, the user may create their own location database or addto or modify the location database to better classify their activities.

In another embodiment, the user may simultaneously wear multiplebiometric monitoring devices (having any of the features describedherein). The biometric monitoring devices of this embodiment maycommunicate with each other or a remote device using wired or wirelesscircuitry to calculate, for example, biometric or physiologic qualitiesor quantities that, for example, may be difficult or inaccurate tocalculate otherwise, such as pulse transit time. The use of multiplesensors may also improve the accuracy and/or precision of biometricmeasurements over the accuracy and/or precision of a single sensor. Forexample, having a biometric tracking device on the waist, wrist, andankle may improve the detection of the user taking a step over that of asingle device in only one of those locations. Signal processing may beperformed on the biometric tracking devices in a distributed orcentralized method to provide measurements improved over that of asingle device. This signal processing may also be performed remotely andcommunicated back to the biometric tracking devices after processing.

In another embodiment, heart rate or other biometric data may becorrelated to a user's food log (a log of foods ingested by a user,their nutritional content, and portions thereof). Food log entries maybe entered into the food log automatically or may be entered by the userthemselves through interaction with the biometric monitoring device (ora secondary or remote device, e.g., a smartphone, in communication withthe biometric monitoring device or some other device, e.g., a server, incommunication with the biometric monitoring device). Information may bepresented to the user regarding the biometric reaction of their body toone or more food inputs. For example, if a user has coffee, their heartrate may rise as a result of the caffeine. In another example, if a userhas a larger portion of food late at night, it may take longer for themto fall asleep than usual. Any combination of food input andcorresponding result in biometrics may be incorporated into such afeedback system.

The fusion of food intake data and biometric data may also enable someembodiments of biometric monitoring device to make an estimation of auser's glucose level. This may be particularly useful for users who havediabetes. With an algorithm which relates the glucose level to theuser's activity (e.g. walking, running, calorie burn) and nutritionalintake, a biometric monitoring device may be able to advise the userwhen they are likely to have an abnormal blood sugar level.

Processing Task Delegation

Embodiments of biometric monitoring devices may include one or moreprocessors. For example, an independent application processor may beused to store and execute applications that utilize sensor data acquiredand processed by one or more sensor processors (processor(s) thatprocess data from physiological, environmental, and/or activitysensors). In the case where there are multiple sensors, there may alsobe multiple sensor processors. An application processor may have sensorsdirectly connected to it as well. Sensor and application processors mayexist as separate discrete chips or exist within the same packaged chip(multi-core). A device may have a single application processor, or anapplication processor and sensor processor, or a plurality ofapplication processors and sensor processors.

In one embodiment, the sensor processor may be placed on a daughterboardthat consists of all of the analog components. This board may have someof the electronics typically found on the main PCB such as, but notlimited to, transimpedance amplifiers, filtering circuits, levelshifters, sample-and-hold circuits, and a microcontroller unit. Such aconfiguration may allow the daughterboard to be connected to the mainPCB through the use of a digital connection rather than an analogconnection (in addition to any necessary power or ground connections). Adigital connection may have a variety of advantages over an analogdaughterboard to main PCB connection, including, but not limited to, areduction in noise and a reduction in the number of necessary cables.The daughterboard may be connected to the main board through the use ofa flex cable or set of wires.

Multiple applications may be stored on an application processor. Anapplication may consist of executable code and data for the application,but is not limited to these. Data may consist of graphics or otherinformation required to execute the application or it may be informationoutput generated by the application. The executable code and data forthe application may both reside on the application processor (or memoryincorporated therein) or the data for the application may be stored andretrieved from an external memory. External memory may include but isnot limited to NAND flash, NOR flash, flash on another processor, othersolid-state storage, mechanical or optical disks, RAM, etc.

The executable code for an application may also be stored in an externalmemory. When a request to execute an application is received by theapplication processor, the application processor may retrieve theexecutable code and/or data from the external storage and execute it.The executable code may be temporarily or permanently stored on thememory or storage of the application processor. This allows theapplication to be executed more quickly on the next execution request,since the step of retrieval is eliminated. When the application isrequested to be executed, the application processor may retrieve all ofthe executable code of the application or portions of the executablecode. In the latter case, only the portion of executable code requiredat that moment is retrieved. This allows applications that are largerthan the application processor's memory or storage to be executed.

The application processor may also have memory protection features toprevent applications from overwriting, corrupting, interrupting,blocking, or otherwise interfering with other applications, the sensorsystem, the application processor, or other components of the system.

Applications may be loaded onto the application processor and/or anyexternal storage via a variety of wired, wireless, optical, orcapacitive mechanisms including, but not limited to, USB, Wi-Fi,Bluetooth, Bluetooth Low Energy, NFC, RFID, Zigbee.

Applications may also be cryptographically signed with an electronicsignature. The application processor may restrict the execution ofapplications to those that have the correct signature.

Integration of Systems in a Biometric Monitoring Device

In some implementations of biometric monitoring devices, some sensors orelectronic systems in the biometric monitoring device may be integratedwith one another or may share components or resources. For example, aphotodetector for an optically-based heart rate sensor (such as may beused in the heart-rate sensors discussed in U.S. Provisional PatentApplication No. 61/946,439, filed Feb. 28, 2014, and previouslyincorporated by reference herein), may also serve as a photodetector fordetermining ambient light level, such as may be used to correct for theeffects of ambient light on the heart rate sensor reading. For example,if the light source for such a heart rate detector is turned off, thelight that is measured by the photodetector may be indicative of theamount of ambient light that is present.

In some implementations of a biometric monitoring device, the biometricmonitoring device may be configured or communicated with using onboardoptical sensors such as the components in an optical heart rate monitor.For example, the photodetectors of an optical heart-rate sensor (or, ifpresent, an ambient light sensor) may also serve as a receiver for anoptically-based transmission channel, e.g., infrared communications.

In some implementations of a biometric monitoring device, a hybridantenna may be included that combines a radio frequency antenna, e.g., aBluetooth antenna or GPS antenna, with an inductive loop, such as may beused in a near-field communications (NFC) tag or in an inductivecharging system. In such implementations, the functionality for twodifferent systems may be provided in one integrated system, savingpacking volume. In such a hybrid antenna, an inductive loop may beplaced in close proximity to the radiator of an inverted-F antenna. Theinductive loop may inductively couple with the radiator, allowing theinductive loop to serve as a planar element of the antenna forradio-frequency purposes, thus forming, for example, a planar inverted-Fantenna. At the same time, the inductive loop may also serve its normalfunction, e.g., such as providing current to an NFC chip throughinductive coupling with an electromagnetic field generated by an NFCreader. Examples of such hybrid antenna systems are discussed in moredetail in U.S. Provisional Patent Application No. 61/948,470, filed Mar.5, 2014, which was previously incorporated herein by reference in the“Cross-Reference to Related Applications” section and which is againhereby incorporated by reference with respect to content directed athybrid antenna structures. Of course, such hybrid antennas may also beused in other electronic devices other than biometric monitoringdevices, and such non-biometric-monitoring-device use of hybrid antennasis contemplated as being within the scope of this disclosure.

Methods of Wearing the Device

Some embodiments of biometric monitoring devices may include a housinghaving a size and shape that facilitates fixing the biometric monitoringdevice to the user's body during normal operation where the device, whencoupled to the user, does not measurably or appreciably impact theuser's activity. The biometric monitoring device may be worn indifferent ways depending on the specific sensor package that isintegrated into the biometric monitoring device and the data that theuser would like to acquire.

A user may wear some embodiments of the biometric monitoring devices ofthe present disclosure on their wrist or ankle (or arm or leg) with theuse of a band that is flexible and thereby readily fitted to the user.The band may have an adjustable circumference, therefore allowing it tobe fitted to the user. The band may be constructed from a material thatshrinks when exposed to heat, therefore allowing the user to create acustom fit. The band may be detachable from the “electronics” portion ofthe biometric monitoring device and, if necessary, replaceable.

In some embodiments, the biometric monitoring device may consist of twomajor components—a body (containing the “electronics”) and a band (thatfacilitates attaching the device to the user). The body may include ahousing (made, for example, of a plastic or plastic-like material) andextension tabs projecting from the body (made, for example, from a metalor metal-like material). (See, for example, FIGS. 2C through 3C). Theband (made, for example, of a thermoplastic urethane) may be attachableto the body, e.g., mechanically or adhesively. The band may extend out afraction of the circumference of the user's wrist. The distal ends ofthe urethane band may be connected with a Velcro or a hook-and-loopelastic fabric band that loops around a D-Ring on one side and thenattaches back to itself. In this embodiment, the closure mechanism mayallow the user infinite band length adjustment (unlike an indexed holeand mechanical clasp closure). The Velcro or elastic fabric may beattached to the band in a manner that allows it to be replaced (forexample, if it is worn or otherwise undesirable to wear before theuseful end of life of the device). In one embodiment, the Velcro orfabric may be attached with screws or rivets and/or glue, adhesives,and/or a clasp to the band.

Embodiments of the biometric monitoring devices of the presentdisclosure may also be integrated into and worn in a necklace, chestband, bra, adhesive patch, glasses, earring, or toe band. Such biometricmonitoring devices may be built in such a way that the sensorpackage/portion of the biometric monitoring device is removable and maybe worn in any number of ways including, but not limited to, thoselisted above.

In another embodiment, embodiments of biometric monitoring devices ofthe present disclosure may be worn clipped to an article of clothing ordeposited in clothing (e.g., pocket) or an accessory (e.g., handbag,backpack, wallet). Because such biometric monitoring devices may not benear the user's skin, in embodiments that include heart ratemeasurements, the measurements may be obtained in a discrete, “ondemand” context by the user manually placing the device into a specificmode (e.g., by depressing a button, covering a capacitive touch sensorwith a fingertip, etc., possibly with the heart rate sensor embedded inthe button/sensor) or automatically once the user places the deviceagainst the skin (e.g., applying the finger to an optical heart ratesensor).

User Interface with the Device

Some embodiments of a biometric monitoring device may includefunctionality for allowing one or more methods of interacting with thedevice either locally or remotely.

In some embodiments, the biometric monitoring device may convey datavisually through a digital display. The physical embodiment of thisdisplay may use any one or a plurality of display technologiesincluding, but not limited to one or more of LED, LCD, AMOLED, E-Ink,Sharp display technology, graphical displays, and other displaytechnologies such as TN, HTN, STN, FSTN, TFT, IPS, and OLET. Thisdisplay may show data acquired or stored locally on the device or maydisplay data acquired remotely from other devices or Internet services.The biometric monitoring device may use a sensor (for example, anAmbient Light Sensor, “ALS”) to control or adjust the amount of screenbacklighting, if backlighting is used. For example, in dark lightingsituations, the display may be dimmed to conserve battery life, whereasin bright lighting situations, the display brightness may be increasedso that it is more easily read by the user.

In another embodiment, the biometric monitoring device may use single ormulticolor LEDs to indicate a state of the device. States that thebiometric monitoring device may indicate using LEDs may include, but arenot limited to, biometric states such as heart rate or applicationstates such as an incoming message or that a goal has been reached.These states may be indicated through the LED's color, the LED being onor off (or in an intermediate intensity), pulsing (and/or rate thereof)of the LEDs, and/or a pattern of light intensities from completely offto highest brightness. In one embodiment, an LED may modulate itsintensity and/or color with the phase and frequency of the user's heartrate.

In some embodiments, the use of an E-Ink display may allow the displayto remain on without the battery drain of a non-reflective display. This“always-on” functionality may provide a pleasant user experience in thecase of, for example, a watch application where the user may simplyglance at the biometric monitoring device to see the time. The E-Inkdisplay always displays content without compromising the battery life ofthe device, allowing the user to see the time as they would on atraditional watch.

Some implementations of a biometric monitoring device may use a lightsuch as an LED to display the heart rate of the user by modulating theamplitude of the light emitted at the frequency of the user's heartrate. The device may depict heart rate zones (e.g., aerobic, anaerobic,etc.) through the color of an LED (e.g., green, red) or a sequence ofLEDs that light up in accordance with changes in heart rate (e.g., aprogress bar). The biometric monitoring device may be integrated orincorporated into another device or structure, for example, glasses orgoggles, or communicate with glasses or goggles to display thisinformation to the user.

Some embodiments of a biometric monitoring device may also conveyinformation to a user through the physical motion of the device. Onesuch embodiment of a method to physically move the device is the use ofa vibration-inducing motor. The device may use this method alone, or incombination with a plurality of other motion-inducing technologies.

In some implementations, a biometric monitoring device may conveyinformation to a user through audio feedback. For example, a speaker inthe biometric monitoring device may convey information through the useof audio tones, voice, songs, or other sounds.

These three information communication methods—visual, motion, andauditory—may, in various embodiments of biometric monitoring devices, beused alone or in any combination with each other or another method ofcommunication to communicate any one or plurality of the followinginformation:

-   -   That a user needs to wake up at certain time    -   That a user should wake up as they are in a certain sleep phase    -   That a user should go to sleep as it is a certain time    -   That a user should wake up as they are in a certain sleep phase        and in a preselected time window bounded by the earliest and        latest time that the user wants to wake up.    -   That an email was received    -   That the user has been inactive for a certain period of time.        Notably, this may integrate with other applications like, for        instance, a meeting calendar or sleep tracking application to        block out, reduce, or adjust the behavior of the inactivity        alert.    -   That the user has been active for a certain period of time    -   That the user has an appointment or calendar event    -   That the user has reached a certain activity metric    -   That the user has gone a certain distance    -   That the user has reached a certain mile pace    -   That the user has reached a certain speed    -   That the user has accumulated a certain elevation gain    -   That the user has taken a certain number of steps    -   That the user has had a heart rate measurement recently    -   That the user's heart rate has reached a certain level    -   That the user has a normal, active, or resting heart rate of a        specific value or in a specific range    -   That the user's heart rate has enter or exited a certain goal        range or training zone    -   That the user has a new heart rate “zone” goal to reach, as in        the case of heart rate zone training for running, bicycling,        swimming, etc. activities    -   That the user has swum a lap or completed a certain number of        laps in a pool    -   An external device has information that needs to be communicated        to the user such as an incoming phone call or any one of the        above alerts    -   That the user has reached a certain fatigue goal or limit. In        one embodiment, fatigue may be determined through a combination        of heart rate, galvanic skin response, motion sensor, and/or        respiration data

These examples are provided for illustration and are not intended tolimit the scope of information that may be communicated by suchembodiments of biometric monitoring devices (for example, to the user).Note that the data used to determine whether or not an alert conditionis met may be acquired from a first device and/or one or more secondarydevices. The biometric monitoring device itself may determine whetherthe criteria or conditions for an alert have been met. Alternatively, acomputing device in communication with the biometric monitoring device(e.g., a server and/or a mobile phone) may determine when the alertshould occur. In view of this disclosure, other information that thebiometric monitoring device may communicate to the user may beenvisioned by one of ordinary skill in the art. For example, thebiometric monitoring device may communicate with the user when a goalhas been met. The criteria for meeting this goal may be based onphysiological, contextual, and environmental sensors on a first device,and/or other sensor data from one or more secondary devices. The goalmay be set by the user or may be set by the biometric monitoring deviceitself and/or another computing device in communication with thebiometric monitoring device (e.g. a server). In an example embodiment,the biometric monitoring device may vibrate when a biometric goal ismet.

Some embodiments of biometric monitoring devices of the presentdisclosure may be equipped with wireless and/or wired communicationcircuitry to display data on a secondary device in real time. Forexample, such biometric monitoring devices may be able to communicatewith a mobile phone via Bluetooth Low Energy in order to give real-timefeedback of heart rate, heart rate variability, and/or stress to theuser. Such biometric monitoring devices may coach or grant “points” forthe user to breathe in specific ways that alleviate stress (e.g. bytaking slow, deep breaths). Stress may be quantified or evaluatedthrough heart rate, heart rate variability, skin temperature, changes inmotion-activity data and/or galvanic skin response.

Some embodiments of biometric monitoring devices may receive input fromthe user through one or more local or remote input methods. One suchembodiment of local user input may use a sensor or set of sensors totranslate a user's movement into a command to the device. Such motionscould include but may not be limited to tapping, rolling the wrist,flexing one or more muscles, and swinging one's arm. Another user inputmethod may be through the use of a button such as, but not limited to,capacitive touch buttons, capacitive screen buttons, and mechanicalbuttons. In one embodiment, the user interface buttons may be made ofmetal. In embodiments where the screen uses capacitive touch detection,it may always be sampling and ready to respond to any gesture or inputwithout an intervening event such as pushing a physical button. Suchbiometric monitoring devices may also take input through the use ofaudio commands. All of these input methods may be integrated intobiometric monitoring devices locally or integrated into a remote devicethat can communicate with such biometric monitoring devices, eitherthrough a wired or wireless connection. In addition, the user may alsobe able to manipulate the biometric monitoring device through a remotedevice. In one embodiment, this remote device may have Internetconnectivity.

Alarms

In some embodiments, the biometric monitoring device of the presentdisclosure may act as a wrist-mounted vibrating alarm to silently wakethe user from sleep. Such biometric monitoring devices may track theuser's sleep quality, waking periods, sleep latency, sleep efficiency,sleep stages (e.g., deep sleep vs REM), and/or other sleep-relatedmetrics through one or a combination of heart rate, heart ratevariability, galvanic skin response, motion sensing (e.g.,accelerometer, gyroscope, magnetometer), and skin temperature. The usermay specify a desired alarm time or window of time (e.g., set alarm togo off between 7 am and 8 am). Such embodiments may use one or more ofthe sleep metrics to determine an optimal time within the alarm windowto wake the user. In one embodiment, when the vibrating alarm is active,the user may cause it to hibernate or turn off by slapping or tappingthe device (which is detected, for example, via motion sensor(s), apressure/force sensor, and/or capacitive touch sensor in the device). Inone embodiment, the device may attempt to arouse the user at an optimumpoint in the sleep cycle by starting a small vibration at a specificuser sleep stage or time prior to the alarm setting. It mayprogressively increase the intensity or noticeability of the vibrationas the user progresses toward wakefulness or toward the alarm setting.(See, for example, FIG. 8).

FIG. 8 illustrates functionality of an example portable biometricmonitoring device smart alarm feature. The biometric monitoring devicemay be able to detect or may be in communication with a device that candetect the sleep stage or state of a user (e.g., light or deep sleep).The user may set a window of time which they would like to be awoken(e.g., 6:15 am to 6:45 am). The smart alarm may be triggered by the usergoing into a light sleep state during the alarm window.

The biometric monitoring device may be configured to allow the user toselect or create an alarm vibration pattern of their choice. The usermay have the ability to “snooze” or postpone an alarm event. In oneembodiment, the user may be able to set the amount of delay for the“snooze” feature—the delay being the amount of time before the alarmwill go off again. They may also be able to set how many times thesnooze feature may be activated per alarm cycle. For example, a user maychoose a snooze delay of 5 minutes and a maximum sequential snoozenumber to be 3. Therefore, they can press snooze up to 3 times to delaythe alarm by 5 minutes each time they press snooze to delay the alarm.In such embodiments, the snooze function will not turn off the alarm ifthe user attempts to press snooze a fourth time.

Some biometric monitoring devices may have information about the user'scalendar and/or schedule. The user's calendar information may be entereddirectly into the biometric monitoring device or it may be downloadedfrom a different device (e.g. a smartphone). This information may beused to automatically set alarms or alarm characteristics. For example,if a user has a meeting at 9 am in the morning, the biometric monitoringdevice may automatically wake the user up at 7:30 am to allow the userenough time to prepare for and/or get to the meeting. The biometricmonitoring device may determine the amount of time required for the userto prepare for the meeting based on the user's current location, thelocation of the meeting, and the amount of time it would take to get thelocation of the meeting from the user's current location. Alternatively,historical data about how long the user takes to get to the meetinglocation and/or prepare to leave for the meeting (e.g. how long it takesto wake up, take a shower, have breakfast, etc. in the morning) may beused to determine at what time to wake the user. A similar functionalitymay be used for calendar events other than meetings such as eatingtimes, sleeping times, napping times, and exercise times.

In some embodiments, the biometric monitoring device may use informationon when the user went to sleep to determine when an alarm should go offto wake the user. This information may supplement calendar informationdescribed herein. The user may have a goal of approximately how manyhours of sleep they would like to get each night or week. The biometricmonitoring device may set the morning alarm at the appropriate time forthe user to meet these sleep goals. In addition to amount of time thatthe user would like to sleep each night, other sleep goals that the usermay set may include, but are not limited to, the amount of deep sleep,REM sleep, and light sleep that the user experiences while sleeping, allof which may be used by the biometric monitoring device to determinewhen to set an alarm in the morning. Additionally, the user may bealerted at night when they should go to bed to meet their sleep goals.Additionally, the user may be alerted during the day when they shouldtake a nap to meet their sleep goals. The time at which to alert a userthat they should take a nap may be determined by factors that optimizethe user's sleep quality during the nap, subsequent naps, or night-timesleep. For example, the user is likely to have a hard time fallingasleep at night if they took a nap in the early evening. The user mayalso be advised to eat certain foods or drinks or avoid certain foods ordrinks to optimize their sleep quality. For example, a user may bediscouraged from drinking alcohol close to their bed time as it islikely to decrease their sleep quality. The user may also be advised toperform certain activities or avoid certain activities to optimize theirsleep quality. For example, a user may be encouraged to exercise in theearly afternoon to improve their sleep quality. A user may bediscouraged from exercising or watching TV close to their bedtime toimprove their sleep quality.

User Interface with a Secondary Device

In some embodiments, the biometric monitoring device may transmit andreceive data and/or commands to and/or from a secondary electronicdevice. The secondary electronic device may be in direct or indirectcommunication with the biometric monitoring device. Direct communicationrefers herein to the transmission of data between a first device and asecondary device without any intermediary devices. For example, twodevices may communicate to one another over a wireless connection (e.g.Bluetooth) or a wired connection (e.g. USB). Indirect communicationrefers to the transmission of data between a first device and asecondary device with the aid of one or multiple intermediary thirddevices which relay the data. Third devices may include, but are notlimited to, a wireless repeater (e.g. WiFi repeater), a computing devicesuch as a smartphone, laptop, desktop or tablet computer, a cell phonetower, a computer server, and other networking electronics. For example,a biometric device may send data to a smartphone which forwards the datathrough a cellular network data connection to a server which isconnected through the internet to the cellular network.

In some embodiments, the secondary device that acts as a user interfaceto the biometric monitoring device may consist of a smartphone. An appon the smart phone may facilitate and/or enable the smartphone to act asa user interface to the biometric monitoring device. The biometricmonitoring device may send biometric and other data to the smartphone inreal-time or with some delay. The smartphone may send a command orcommands to the biometric monitoring device, for example, to instruct itto send biometric and other data to the smartphone in real-time or withsome delay. For example, if the user enters a mode in the app fortracking a run, the smartphone may send a command to the biometricdevice to instruct it to send data in real-time. Therefore, the user cantrack their run on their app as they go along without any delay.

Such a smartphone may have one or multiple apps to enable the user toview data from their biometric device or devices. The app may, bydefault, open to a “dashboard” page when the user launches or opens theapp. On this page, summaries of data totals such as the total number ofsteps, floors climbed miles traveled, calories burned, calories consumedand water consumed may be shown. Other pertinent information such as thelast time the app received data from the biometric monitoring device,metrics regarding the previous night's sleep (e.g. when the user went tosleep, woke up, and how long they slept for), and how many calories theuser can eat in the day to maintain their caloric goals (e.g. a caloriedeficit goal to enable weight loss) may also be shown. The user may beable to choose which of these and other metrics are shown on thedashboard screen. The user may be able to see these and other metrics onthe dashboard for previous days. They may be able to access previousdays by pressing a button or icon on a touchscreen. Alternatively,gestures such as swiping to the left or right may enable the user tonavigate through current and previous metrics.

The smartphone app may also have another page which provides a summaryof the user's activities. Activities may include, but are not limitedto, walking, running, biking, cooking, sitting, working, swimming,working out, weightlifting, commuting, and yoga. Metrics pertinent tothese activities may be presented on this page. For example, a bar graphmay show how the number of steps the user took for different portions ofthe day (e.g. how many steps every 5 minutes or 1 hour). In anotherexample, the amount of time the user spent performing a certain activityand how many calories were burned in this period of time may bedisplayed. Similar to the dashboard page, the app may providenavigational functionality to allow the user to see these and othermetrics for past days. Other time periods such as an hour, minute, week,month or year may also be selected by the user to enable them to viewtrends and metrics of their activities over shorter or larger spans oftime.

The smartphone app may also have an interface to log food that has been,or will be, eaten by the user. This interface may have a keyword searchfeature to allow the user to quickly find the food that they would liketo enter into their log. As an alternative to, or in addition to,searching for foods, users may have the ability to find a food to log bynavigating through a menu or series of menus. For example, a user maychoose the following series ofcategories—breakfast/cereal/healthy/oatmeal to arrive at the food whichthey would like to log (e.g., apple-flavored oatmeal). At any one ofthese menus, the user may be able to perform a keyword search. Forexample, the user may search for “oatmeal” after having selected thecategory “breakfast” to search for the keyword “oatmeal” within thecategory of breakfast foods. After having selected the food that theywould like to log, the user may be able to modify or enter the servingsize and nutritional content. After having logged at least one food, theapp may display a summary of the foods that were logged in a certaintime period (e.g. a day) and the nutritional content of the foods(individual and total calorie content, vitamin content, sugar content,etc.).

The smartphone app may also have a page that displays metrics regardingthe user's body such as the user's weight, body fat percentage, BMI, andwaist size. It may display a graph or graphs showing the trend of one ormultiple of these metrics over a certain period of time (e.g., twoweeks). The user may be able to choose the value of this period of timeand view previous time periods (e.g., last month).

The smartphone app may also have a page which allows the user to enterhow much water the user has consumed. Each time the user drinks somewater, they may enter that amount in the unit of their choice (e.g.,ozs., cups, etc.). The app may display the total of all of the water theuser has logged within a certain time period (e.g., a day). The app mayallow the user to see previously-logged water entries and daily totalsfor previous days as well as the current day.

The smartphone app may also have a page that displays online friends ofthe user. This “friends” page may enable the user to add or request newfriends (e.g., by searching for their name or by their email address).This page may also display a leaderboard of the user and his or herfriends. The user and his or her friends may be ranked based on one ormore metrics. For example, the user and his or her friends may be rankedusing the total of the past seven days' step counts.

The smartphone app may also have a page that shows metrics regarding theuser's sleep for the previous night and/or previous nights. This pagemay also enable the user to log when they slept in the past byspecifying when they went to bed and when they woke. The user may alsohave the ability to enter a subjective metric about their sleep (e.g.,bad night's rest, good night's rest, excellent night's rest, etc.). Theuser may be able to view these metrics for days or time periods (e.g.,two weeks) in the past. For example, the sleep page may default toshowing a bar graph of the amount of time the user slept each night inthe last two weeks. The user may be able to also view a bar graph of theamount of time the user slept each night in the last month.

The user may also be able to access the full capabilities of thesmartphone app described herein (e.g., the ability to enter food logs,view dashboard, etc.) through an alternative or additional interface. Inone embodiment, this alternative interface may consist of a webpage thatis hosted by a server in indirect communication with the biometricmonitoring device. The webpage may be accessed through any internetconnected device using a program such as a web browser.

Wireless Connectivity and Data Transmission

Some embodiments of biometric monitoring devices of the presentdisclosure may include a mechanism of wireless communication to transmitand receive information from the Internet and/or other devices. Thewireless communication may consist of one or more interfaces such asBluetooth, ANT, WLAN, power-line networking, and cell phone networks.These are provided as examples and should not be understood to excludeother existing wireless communication methods or protocols, or wirelesscommunications techniques or protocols that are yet to be invented.

The wireless connection may be bi-directional. The biometric monitoringdevice may transmit, communicate and/or push its data to other devices,e.g., smart phones, computers, etc., and/or the Internet, e.g., webservers and the like. The biometric monitoring device may also receive,request and/or pull data from other devices and/or the Internet.

The biometric monitoring device may act as a relay to providecommunication for other devices to each other or to the Internet. Forexample, the biometric monitoring device may connect to the Internet viaWLAN but also be equipped with an ANT radio. An ANT device maycommunicate with the biometric monitoring device to transmit its data tothe Internet through the biometric monitoring device's WLAN (and viceversa). As another example, the biometric monitoring device may beequipped with Bluetooth. If a Bluetooth-enabled smart phone comes withinrange of the biometric monitoring device, the biometric monitoringdevice may transmit data to, or receive data from, the Internet throughthe smart phone's cell phone network. Data from another device may alsobe transmitted to the biometric monitoring device and stored (or viceversa) or transmitted at a later time.

Embodiments of biometric monitoring devices of the present disclosuremay also include functionality for streaming or transmitting web contentfor display on the biometric monitoring device. The following aretypical examples of such content:

-   -   1. Historical graphs of heart rate and/or other data measured by        the device but stored remotely    -   2. Historical graphs of user activity and/or foods consumed        and/or sleep data that are measured by other devices and/or        stored remotely (e.g., such as at a website like fitbit.com)    -   3. Historical graphs of other user-tracked data that are stored        remotely. Examples include heart rate, blood pressure, arterial        stiffness, blood glucose levels, cholesterol, duration of TV        watching, duration of video game play, mood, etc.    -   4. Coaching and/or dieting data based on one or more of the        user's heart rate, current weight, weight goals, food intake,        activity, sleep, and other data.    -   5. User progress toward heart rate, weight, activity, sleep,        and/or other goals.    -   6. Summary statistics, graphics, badges, and/or metrics (e.g.,        “grades”) to describe the aforementioned data    -   7. Comparisons between the aforementioned data for the user and        similar data for his/her “friends” with similar devices and/or        tracking methods    -   8. Social content such as Twitter feeds, instant messaging,        and/or Facebook updates    -   9. Other online content such as newspaper articles, horoscopes,        weather reports, RSS feeds, comics, crossword puzzles,        classified advertisements, stock reports, and websites    -   10. Email messages and calendar schedules

Content may be delivered to the biometric monitoring device according todifferent contexts. For instance, in the morning, news and weatherreports may be displayed along with the user's sleep data from theprevious night. In the evening, a daily summary of the day's activitiesmay be displayed.

Various embodiments of biometric monitoring devices as disclosed hereinmay also include NFC, RFID, or other short-range wireless communicationcircuitry that may be used to initiate functionality in other devices.For instance, a biometric monitoring device may be equipped with an NFCantenna so that when a user puts it into close proximity with a mobilephone, an app is launched automatically on the mobile phone.

These examples are provided for illustration and are not intended tolimit the scope of data that may be transmitted, received, or displayedby the device, nor any intermediate processing that may occur duringsuch transfer and display. In view of this disclosure/application, manyother examples of data that may be streamed to or via a biometricmonitoring device may be envisioned by one reasonably skilled in theart.

Charging and Data Transmission

Some embodiments of biometric monitoring devices may use a wiredconnection to charge an internal rechargeable battery and/or transferdata to a host device such as a laptop or mobile phone. In oneembodiment, similar to one discussed earlier in this disclosure, thebiometric monitoring device may use magnets to help the user align thebiometric monitoring device to a dock or cable. The magnetic field ofmagnets in the dock or cable and the magnets in the device itself may bestrategically oriented so as to force the biometric monitoring device toself-align with the dock or cable (or, more specifically, a connector onthe cable) and so as to provide a force that holds the biometricmonitoring device in the dock or to the cable. The magnets may also beused as conductive contacts for charging or data transmission purposes.In another embodiment, a permanent magnet may only be used in the dockor cable side and not in the biometric monitoring device itself. Thismay improve the performance of the biometric monitoring device where thebiometric monitoring device employs a magnetometer. If there is a magnetin the biometric monitoring device, the strong field of a nearbypermanent magnet may make it significantly more difficult for themagnetometer to accurately measure the earth's magnetic field. In suchembodiments, the biometric monitoring device may utilize a ferrousmaterial in place of a magnet, and the magnets on the dock or cable sidemay attach to the ferrous material.

In another embodiment, the biometric monitoring device may contain oneor more electromagnets in the biometric monitoring device body. Thecharger or dock for charging and data transmission may also contain anelectromagnet and/or a permanent magnet. The biometric monitoring devicecould only turn on its electromagnet when it is close to the charger ordock. The biometric monitoring device may detect proximity to the dockor charger by looking for the magnetic field signature of a permanentmagnet in the charger or dock using a magnetometer. Alternatively, thebiometric monitoring device may detect proximity to the charger bymeasuring the Received Signal Strength Indication (RSSI) of a wirelesssignal from the charger or dock, or, in some embodiments, by recognizingan NFC or RFID tag associated with the charger or dock. Theelectromagnet could be reversed, creating a force that repels the devicefrom the charging cable or dock either when the device doesn't need tobe charged, synced, or when it has completed syncing or charging. Insome embodiments, the charger or dock may include the electromagnet andmay be configured (e.g., a processor in the charger or dock may beconfigured via program instructions) to turn the electromagnet on when abiometric monitoring device is connected for charging (the electromagnetmay normally be left on such that a biometric monitoring device that isplaced on the charger is drawn against the charger by the electromagnet,or the electromagnet may be left off until the charger determines that abiometric monitoring device has been placed on the charger, e.g.,through completion of a charging circuit, recognition of an NFC tag inthe biometric monitoring device, etc., and then turned on to draw thebiometric monitoring device against the charger. Upon completion ofcharging (or of data transfer, if the charger is actually a datatransfer cradle or a combined charger/data transfer cradle), theelectromagnet may be turned off (either temporarily or until thebiometric monitoring device is again detected as being placed on thecharger) and the biometric monitoring device may stop being drawnagainst the charger. In such embodiments, it may be desirable to orientthe interface between the biometric monitoring device and the chargersuch that, in the absence of a magnetic force generated by theelectromagnet, the biometric monitoring device would fall off of thecharger or otherwise shift into a visibly different position from thecharging position (to visually indicate to a user that charging or datatransfer is complete).

Sensor Use in Data Transfer

In some implementations, biometric monitoring devices may include acommunications interface that may switch between two or more protocolsthat have different data transmission rates and different powerconsumption rates. Such switching may be driven by data obtained fromvarious sensors of the biometric monitoring device. For example, ifBluetooth is used, the communications interface may switch between usingBluetooth base rate/enhanced data rate (BR/EDR) and Bluetooth low energy(BLE) protocols responsive to determinations made based on data from thesensors of the biometric monitoring device. For example, thelower-power, slower BLE protocol may be used when sensor data fromaccelerometers in a biometric monitoring device indicates that thewearer is asleep or otherwise sedentary. By contrast, the higher-power,faster BR/EDR protocol may be used when sensor data from theaccelerometers in a biometric monitoring device indicates that thewearer is walking around. Such adaptive data transmission techniques andfunctionality are discussed further in U.S. Provisional PatentApplication No. 61/948,468, filed Mar. 5, 2014, which was previouslyincorporated herein by reference in the “Cross-Reference to RelatedApplications” section and which is again hereby incorporated byreference with respect to content directed at adaptive data transferrates in biometric monitoring devices.

Such communication interfaces may also serve as a form of sensor for abiometric monitoring device. For example, a wireless communicationsinterface may allow a biometric monitoring device to determine thenumber and type of devices that are within range of the wirelesscommunications interface. Such data may be used to determine if thebiometric monitoring device is in a particular context, e.g., indoors,in a car, etc., and to change its behavior in various ways in responseto such a determination. For example, as discussed in U.S. ProvisionalPatent Application No. 61/948,468 (incorporated by reference above),such contexts may be used to drive the selection of a particularwireless communications protocol to use for wireless communications.

Configurable App Functionality

In some embodiments, biometric monitoring devices of the presentdisclosure may include a watch-like form factor and/or a bracelet,armlet, or anklet form factor and may be programmed with “apps” thatprovide specific functionality and/or display specific information. Appsmay be launched or closed by a variety of mechanisms including, but notlimited to, pressing a button, using a capacitive touch sensor,performing a gesture that is detected by an accelerometer, moving to aspecific location or area detected by a GPS or motion sensor,compressing the biometric monitoring device body (thereby creating apressure signal inside the device that may be detected by an altimeterinside the biometric monitoring device), or placing the biometricmonitoring device close to an NFC tag that is associated with an app orset of apps. Apps may also be automatically triggered to launch or closeby certain environmental or physiological conditions including, but notlimited to, detection of a high heart rate, detection of water using awet sensor (to launch a swimming application, for example), a certaintime of day (to launch a sleep tracking application at night, forexample), a change in pressure and motion characteristic of a planetaking off or landing to launch and close an “airplane” mode app. Appsmay also be launched or closed by meeting multiple conditionssimultaneously. For example, if an accelerometer detects that a user isrunning and the user presses a button, the biometric monitoring devicemay launch a pedometer application, an altimeter data collectionapplication, and/or display. In another case where the accelerometerdetects swimming and the user presses the same button, it may launch aswimming lap-counting application.

In some embodiments, the biometric monitoring device may have aswim-tracking mode that may be launched by starting a swimming app. Inthis mode, the biometric monitoring device's motion sensors and/ormagnetometer may be used to detect swim strokes, classify swim stroketypes, detect swimming laps, and other related metrics such as strokeefficiency, lap time, speed, distance, and calorie burn. Directionalchanges indicated by the magnetometer may be used to detect a diversityof lap turn methods. In a preferred embodiment, data from a motionsensor and/or pressure sensor may be used to detect strokes.

In another embodiment, a bicycling app may be launched by moving thebiometric monitoring device within proximity of an NFC or RFID tag thatis located on the bicycle, on a mount on the bicycle, or in a locationassociated with a bicycle including, but not limited to, a bike rack orbike storage facility. (See, for example, FIG. 10). The app launched mayuse a different algorithm than is normally used to determine metricsincluding, but not limited to, calories burned, distance travelled, andelevation gained. The app may also be launched when a wireless bikesensor is detected including, but not limited to, a wheel sensor, GPS,cadence sensor, or power meter. The biometric monitoring device may thendisplay and/or record data from the wireless bike sensor or bikesensors.

Additional apps include, but are not limited to, a programmable orcustomizable watch face, stop watch, music player controller (e.g., mp3player remote control), text message and/or email display or notifier,navigational compass, bicycle computer display (when communicating witha separate or integrated GPS device, wheel sensor, or power meter),weight-lifting tracker, sit-up reps tracker, pull up reps tracker,resistance training form/workout tracker, golf swing analyzer, tennis(or other racquet sport) swing/serve analyzer, tennis game swingdetector, baseball swing analyzer, ball throw analyzer (e.g., football,baseball), organized sports activity intensity tracker (e.g., football,baseball, basketball, volleyball, soccer), disk throw analyzer, foodbite detector, typing analyzer, tilt sensor, sleep quality tracker,alarm clock, stress meter, stress/relaxation biofeedback game (e.g.,potentially in combination with a mobile phone that provides auditoryand/or visual cues to train user breathing in relaxation exercises),teeth brushing tracker, eating rate tracker (e.g., to count or track therate and duration by which a utensil is brought to the mouth for foodintake), intoxication or suitability to drive a motor vehicle indicator(e.g., through heart rate, heart rate variability, galvanic skinresponse, gait analysis, puzzle solving, and the like), allergy tracker(e.g., using galvanic skin response, heart rate, skin temperature,pollen sensing and the like (possibly in combination with externalseasonal allergen tracking from, for instance, the internet and possiblydetermining the user's response to particular forms of allergen, e.g.,tree pollen, and alerting the user to the presence of such allergens,e.g., from seasonal information, pollen tracking databases, or localenvironmental sensors in the biometric monitoring device or employed bythe user), fever tracker (e.g., measuring the risk, onset, or progressof a fever, cold, or other illness, possibly in combination withseasonal data, disease databases, user location, and/or user providedfeedback to assess the spread of a particular disease (e.g., flu) inrelation to a user, and possibly prescribing or suggesting theabstinence of work or activity in response), electronic games, caffeineaffect tracker (e.g., monitoring the physiologic response such as heartrate, heart rate variability, galvanic skin response, skin temperature,blood pressure, stress, sleep, and/or activity in either short term orlong term response to the intake or abstinence of coffee, tea, energydrinks and/or other caffeinated beverages), drug affect tracker (e.g.,similar to the previously mentioned caffeine tracker but in relation toother interventions, whether they be medical or lifestyle drugs such asalcohol, tobacco, etc.), endurance sport coach (e.g., recommending orprescribing the intensity, duration, or profile of arunning/bicycling/swimming workout, or suggesting the abstinence ordelay of a workout, in accordance with a user specified goal such as amarathon, triathlon, or custom goal utilizing data from, for instance,historical exercise activity (e.g., distance run, pace), heart rate,heart rate variability, health/sickness/stress/fever state), weightand/or body composition, blood pressure, blood glucose, food intake orcaloric balance tracker (e.g., notifying the user how many calories hemay consume to maintain or achieve a weight), pedometer, and nail bitingdetector. In some cases, the apps may rely solely on the processingpower and sensors of the present disclosure. In other cases, the appsmay fuse or merely display information from an external device or set ofexternal devices including, but not limited to, a heart rate strap, GPSdistance tracker, body composition scale, blood pressure monitor, bloodglucose monitor, watch, smart watch, mobile communication device such asa smart phone or tablet, or server.

In one embodiment, the biometric monitoring device may control a musicplayer on a secondary device. Aspects of the music player that may becontrolled include, but are not limited to, the volume, selection oftracks and/or playlists, skipping forward or backward, fast forwardingor rewinding of tracks, the tempo of the track, and the music playerequalizer. Control of the music player may be via user input orautomatic based on physiological, environmental, or contextual data. Forexample, a user may be able to select and play a track on their smartphone by selecting the track through a user interface on the biometricmonitoring device. In another example, the biometric monitoring devicemay automatically choose an appropriate track based on the activitylevel of the user (the activity level being calculated from biometricmonitoring device sensor data). This may be used to help motivate a userto maintain a certain activity level. For example, if a user goes on arun and wants to keep their heart rate in a certain range, the biometricmonitoring device may play an upbeat or higher tempo track if theirheart rate is below the range which they are aiming for.

Automated Functions Triggered by User's Activity Sleep Stage TriggeredFunctionality

Sleep stages can be monitored through various biometric signals andmethods disclosed herein, such as heart rate, heart rate variability,body temperature, body motions, ambient light intensity, ambient noiselevel, etc. Such biometrics may be measured using optical sensors,motion sensors (accelerometers, gyroscopic sensors, etc.), microphones,and thermometers, for example, as well as other sensors discussedherein.

The biometric monitoring device may have a communication module as well,including, but not limited to, Wi-Fi (802.xx), Bluetooth (Classic, lowpower), or NFC. Once the sleep stages are estimated, the sleep stagesmay be transmitted to a cloud-based system, home server, or main controlunit that is connected to communication-enabled appliances (with Wi-Fi,Bluetooth, or NFC) wirelessly. Alternatively, the biometric monitoringdevice may communicate directly with the communication-enabledappliances. Such communication-enabled appliances may include, forexample, kitchen appliances such as microwaves, ovens, coffeegrinders/makers, toasters, etc.

Once the sleep stages indicate that it is close the time for the user towake up, the biometric monitoring device may send out a trigger to theappliances that the user has indicated should be operated automatically.For example, the coffee grinder and maker may be caused to start makingcoffee, and the toaster may be caused to start warming up bread. Themicrowave oven may be caused to start cooking oatmeal or eggs as well,and electric kettle to start boiling water. So long as the ingredientsare appropriately prepared, this automated signal may triggerbreakfast-cooking.

Alertness Detection

Alertness, e.g., a low alertness may correlate with a person beingdrowsy, may also be detected from the biometrics listed above, and maybe used to trigger an appliance such as a coffee maker to start brewingcoffee automatically.

Hydration

The portable biometric monitoring device in combination with an activitylevel tracker may submit the user's activity level to a cloud-basedsystem, home server, main control unit, or appliances directly. This maytrigger some actions of the appliances, especially related to hydration,such as starting the ice cube maker of a refrigerator, or loweringoperating temperature of a water purifier.

Power Saving

Many appliances typically operate in alow-power idle state that consumespower. Using aggregated information of the user's biometric signals,communication-enabled appliances may be caused to go into a super-lowpower mode. For example, a water dispenser at home may shut itself downinto a super-low-power mode when the user is asleep or out for work, andmay start cooling/heating water once the user's activity at home isexpected.

Restaurant Recommendation System Based on Location and Activity

Aggregation of real-time biometric signals and location information maybe used to create an educated-guess on one or multiple users' needs fora given time, e.g., ionized drink. Combining this guessed need withhistorical user data on the user's activity levels, activity types,activity time, and activity durations, as well as food intake datalogged by the users, an app on a smart phone and/or smart watch mayrecommend a restaurant that would meet the user's life-style and currentneed.

For example, a user who just finished a six mile circuit may launch thisapp. The app may know that this person maintained a high activity levelfor the past hour, and thus determine that the person may be dehydrated.From the historical user data, the app may also know, for example, thatthe user's diet is heavy on vegetables but low in sugar. With anoptimization algorithm that considers the user's current location, priceranges, and other factors mentioned above, the app may recommend arestaurant that offers smoothies, for example.

Swim Tracking

In some embodiments of a biometric tracking device, the biometrictracking may include a swimming algorithm that may utilize data from oneor more motion sensors, altitude sensors (e.g., such as a barometricpressure sensor), orientation sensors (e.g., magnetometer), locationservice sensor (e.g., GPS, wireless triangulation), and/or temperaturesensors. The sensors may be embedded in a single device mounted to, forinstance, the wrist. In other embodiments, extra sensor devices may beattached to the swimmer's forehead, back of the head, goggles, back,hip, shoulder, thighs, legs, and/or feet.

Three potential functional components of swimming exercise analysis areas follows:

-   -   Stroke count detection—provides stroke counts per lap, where a        lap is defined to be a one-way traverse from one end of the pool        to the opposite end.    -   Stroke type classification—describes the swimming stroke type of        the user (e.g., crawl stroke, breast stroke, back stroke,        butterfly stroke, side stroke, kicking without strokes, body        streamline, etc.) and can be any or a combination of:        -   a. Classification of each stroke that a user takes        -   b. Classification of the predominant stroke type used per            complete lap.        -   c. Classification of stroke type used per fractional lap            (e.g. half a lap of freestyle, half a lap of breast stroke)    -   Lap count—counts the laps traversed by the user. One method of        determining a lap is by detecting when the user turns in a pool.

Turning is defined to be a 180 degree change in heading direction. As aturn is detected, start and end of a lap may be inferred. Taking a break(no motion for a certain period of time) at a point in the pool(typically at one end or the other) before starting to swim again isalso considered a turn as long as the following heading direction isopposite the heading prior to the break.

In some embodiments, these functional components may be combined in amultitude of ways.

Algorithm Structure

The three functional components of the swimming exercise analysis may beperformed sequentially, in parallel, or in hybrid order (a combinationof some sequential blocks and some parallel blocks).

Sequential Approach (See FIG. 15A)

In one embodiment, raw and/or pre-processed sensor signals may first beanalyzed by a stroke detector algorithm. The stroke detector algorithmmay use temporal peaks (local maxima and/or local minima) in a motionsensor (e.g., accelerometer, gyroscope) as an indication that a strokehas been taken. Then one or more heuristic rules may also be applied toremove peaks that do not represent strokes. For example, the magnitudesof the peaks, temporal distance of two adjacent peaks, peak-to-peakamplitude, and/or morphological characteristics of the peaks (e.g.,sharpness) may indicate that certain peaks do not represent strokes.When sensors provide more than one dimensional data, e.g., such as3-axis accelerometers, or 3 axis motion sensors+altimeter (totaling4-axis data), timings and relevant sizes of peaks in all axes may betaken into account to determine whether or not the peaks in one or moreof the axes are generated by a stroke or not.

If a single peak representing a stroke or group of peaks from multipledata axes representing strokes are observed, features may be extractedfrom a segment of data that are obtained from the time between when theprevious peak is detected and when the current peak is detected.Features include, but are not limited to, maximum and minimum values,number of ripples in the segment, powers measured in various metrics,e.g., L1 power and L2 power, standard deviation, mean, etc. Theextracted features may then be put through a machine learning systemwhere the system coefficients are computed off-line (supervisedlearning) or are adapted as the user uses the biometric monitoringdevice (unsupervised learning). The machine learning system may thenreturn a stroke classification for each detected stroke.

The turn-detector algorithm may search for sudden changes in motion bycalculating derivatives, moving average, and/or using high-passfiltering on the signals of the sensors (the sensors including, but notlimited to, those listed in this disclosure). Principal ComponentAnalysis (PCA) can also and/or alternatively be performed on thesignal(s). If one principle component is different from thesub-sequential one, then it may be determined that a turn occurred.Whole or partial coefficients of a transform, such as the Fast FourierTransform (FFT) may be used as features as well. Parametric models suchas Autoregressive (AR) models may also be used. Time-varying modelparameters may then be estimated using Linear Prediction Analysis (LPA),Least Mean Squares filtering (LMS), Recursive Least Squares filtering(RLS), and/or Kalman filtering. Estimated model parameters are thencompared to determine if there is an abrupt change in their values.

In one embodiment, the skill level and/or swimming styles (e.g., speed)of the swimmer may be inferred from sensor data, and then used in turndetection. For example, advanced swimmers typically have more powerfulstrokes (i.e., large accelerometer peak magnitudes) and take fewerstrokes to complete a lap. Therefore, metrics that estimate theswimmer's skill level or characteristics may be used in a turn detectionalgorithm. These metrics may include, but are not limited to averagedmotion signals, or integrated motion signals in particular armmovements, estimated heading speed, and detected patterns of an advancedswimmer in motion signals. The swimmer's skill level or othercharacteristics may also be determined through user input. For example,the user may input that they are an advanced, intermediate, or beginnerswimmer.

One or many (combined) features from these analyses may be used todetect if a given data sample, and/or neighboring data samples, havecharacteristics of a turn. To obtain the optimal combination of thefeatures and decision boundary, one can utilize machine learningtechniques such as logistic regression, decision tree, neural nets, etc.

In some embodiments, if a turn is detected, the swimming data accruedsince the previous turn may be summarized, such as the number ofstrokes, stroke type for each stroke and for the lap, split time, etc.If no turn is detected, the stroke counter and type may be updated.Unless the user quits swimming, the algorithm may go back to strokecount detection.

Parallel Approach (See FIG. 15B)

In the parallel approach, some or all of the three functional componentsmay be executed in parallel. For example, stroke-type detection and turndetection may be performed jointly, while stroke count detection is runindependently.

In such embodiments, two functional components, stroke-type and turndetection, may be implemented in a single algorithm that simultaneouslydetects stroke-types and turns. For example, a classifier of swimmingstroke types, e.g., movement analysis that detects free style strokes,breast stroke strokes, back strokes, butterfly strokes, and of turntypes (e.g. tumble turn, flip turn, two hand touch) may return adetected type of stroke or a type of detected turn. During thedetection, temporal as well as spectral features may be extracted. Amoving window may first be applied to multiple axes of data. Statisticsof this windowed segment may then be computed, namely, maximum andminimum value, number of ripples in the segment, powers measured invarious metrics (e.g., L1 power and L2 power, standard deviation, mean).Independent component analysis (ICA) and/or principal component analysis(PCA) can be applied as well to find any hidden signals that betterrepresent turn-type and stroke-type characteristics. Temporal featuresmay then be computed from this (potentially improved) signalrepresentation. For temporal features, various nonparametric filteringschemes, low-pass filtering, band-pass filtering, high-pass filtering,may be applied to enhance desired signal characteristics.

Spectral analysis such as FFT, wavelet transform, Hilbert transform,etc., may be applied to this windowed segment as well. Whole or partialtransform coefficients may be chosen as features. Parametric models suchas AR, moving average (MA), or ARMA (autoregressive and moving average)models may be used, and the parameters of such a model may be found viaautocorrelation and/or partial autocorrelation, or LPA, LMS, RLS, orKalman filter. The entire or part of estimated coefficients may be usedas features.

Different lengths of moving average windows may be run in parallel, andprovide features listed above, and the whole or part of the features maybe utilized as features as well.

Machine-learned coefficients (supervised learning) may then be appliedto these extracted features. One or more machine learning techniques,namely multiple layers of binomial linear discriminant analysis (e.g.,logistic regression), multinomial logistic regression, neural net,decision tree/forest, or support vector machine, can be trained, andthen used.

As the window of interest moves, the features may be extracted and thesenewly-extracted features will return either a stroke type or detectedturn via a machine learning system.

The stroke detector algorithm may run in parallel independent of stroketype and turn detection. Temporal peaks of raw or pre-filtered sensorsignals may be detected and chosen by heuristic rules.

At the summarizing stage (the stage where metrics regarding the swim maybe determined, displayed, and/or stored) of the algorithm,post-processing may be applied to the sequence of stroke type and turndetections. If a turn is confirmed with certain confidence, the swimmingmetric data from the previous turn may be summarized along with strokecounts detected. If no turn is confirmed, the moving average window mayproceed. Until the user stops swimming, the algorithm may continue toupdate swimming metrics regarding the exercise of the user, including,but not limited to, a total number of turns, total number of laps, totalnumber of strokes, average strokes per lap, number of strokes in thelast lap, the change in number of strokes per lap, etc.

Hybrid Approach (See FIGS. 15C and 15D)

In a hybrid approach, the stroke type and stroke count detection may berun in parallel, followed by turn detection.

Stroke-type detection may return a stroke type via machine learnedcoefficients. A first moving window may take segments of sensor signals.Then features, either entire features or a subset of the moving windowfeatures listed in herein, may be extracted. The machine learningcoefficients, trained off-line, may then be applied to the features todetermine which stroke-type generated the given segments of sensorsignals.

Along with stroke type detection, stroke count detection may be runsimultaneously.

Once the stroke type and counts are detected, turn detection may beperformed with either the entire feature or a subset of the featureslisted.

If a turn is detected, completion of a lap may be recorded in theswimming summary metrics of the user. A post process may be applied todetected stroke types to determine the most prominent stroke type forthe completed lap. Then the algorithm may move to the stroke-type andcount detection stages unless the user stops swimming. If no turn isdetected, the algorithm may continue updating stroke types and counts ofthe current lap until a turn is detected.

Blood Glucose Level and Heart Rate

Biometric monitoring devices that continuously measure biometric signalsmay provide meaningful information on preconditions of, progresstowards, and recoveries from diseases. Such biometric monitoring devicesmay have sensors and run algorithms accordingly to measure and calculatebiometric signals such as heart rate, heart rate variability, stepstaken, calories burned, distance traveled, weight and body fat, activityintensity, activity duration and frequency, etc. In addition to themeasured biometric signals, food intake logs provided by users may beused.

In one embodiment, a biometric monitoring device may observe heart rateand its changes over time, especially before and after a food intakeevent or events. It is known that heart rate is affected by blood sugarlevel, whereas it is well known that high blood sugar level is apre-diabetic condition. Thus, mathematical models that describe therelation between time elapsed (after food intake) and blood sugar levelmay be found via statistical regression, where data are collected fromnormal, pre-diabetic, and diabetic individuals to provide respectivemathematical models. With the mathematical models, one may predictwhether an individual with specific heart rate patterns is healthy,pre-diabetic, or diabetic.

Knowing that many heart failures are associated with pre-diabetic ordiabetic conditions, it is possible to further inform users of biometricmonitoring devices with possible heart failures, e.g., coronary heartdisease, cerebrovascular disease and peripheral vascular disease etc.,of such risks based on their biometric data.

Users' activity intensity, type, duration, and frequency may also betaken into account, when developing the mathematical models, as anargument that controls “probability” of the disease onset, usingrecommended exercise guidelines such as guidelines provided by AmericanHeart Association (http://www.heart.org/). Many guidelines on nutritionand weight management are also available in academia and to the generalpublic to prevent cardiovascular and diabetic disease. Such guidelinesmay be incorporated into the mathematical models with the user dataaccumulated over time, such as ingredients of the food that the usersconsumed, and weight and body fat trends.

If users have set their family members as their friends on a socialnetwork site, which stores and displays biometric data, the likelihoodof the family members getting a disease may also be analyzed and theusers informed of the results.

In addition to informing users regarding a potential development ofdisease, recommended life-style including exercise regime and recipeswith healthier ingredients and methods of preparation may be provided tothe users.

Unification of Grocery Shopping, Cooking, and Food Logging GroceryOrganizing and Recipe Recognition System

Receipts from grocery shopping may contain copious information,especially regarding an individual's eating habits. A novel system thatcombines information from grocery store receipts with an individual'sbiometric data, as collected by a biometric monitoring device, forexample, is presented here. The system may collect and analyze data(information) regarding an individual, and may then recommend optionsthat may change the individual's life-style so as to improve theirhealth. The implementation of this system may involve cloud computing,hardware platform development for sensing and interface, andmobile/website site development.

In one embodiment, when a user checks out at a grocery store, the listof groceries (as obtained from the receipt or, for example, from anemail receipt or invoice) may be transmitted automatically to a remotedatabase (e.g., a cloud server), that may also store the user'sbiometric data. When the user gets home and organizes items in theirrefrigerator and/or pantry, an app on their smart phone/watch mayrecommend which items in the pantry or refrigerator to throw away basedon historical data on food items (e.g., if food items are expired orlikely to have gone bad). Alerts indicating when food has expired orthat it should be consumed in the near future to avoid spoilage may beautomatically sent to the user independently of such activity. Forexample, these alerts may be sent out to the user whenever a certainthreshold has been met (e.g., in two days the milk will expire). Thealerts may also be sent to the user through mechanisms other thanthrough a smart phone/watch. For example, the alerts may be presented tothe user through a web interface, through email, through an alert on alaptop computer, on a tablet computer, desktop computer, or any otherelectronic device which is in direct or indirect communication with thecomputer which maintains and/or analyzes the database of food

Using the updated list of food items, and based on the user's historicalfood consumption data, the app may recommend recipes to the user. In oneembodiment, preference may be given to recipes that use the items whatshould be eaten first (e.g., before they expire, go bad, or become lessfresh faster than other ingredients). To recommend the optimal recipethat is nutritionally balanced, correctly portioned, and tailored to theuser's activity, the app may also analyze the user's activity data aswell. For example, if the user lifted weights in the morning,high-protein meals may be recommended. In another example, if the userwas not very active, the size of the recipe may be decreased to lowerthe number of calories that the final meal contains.

Note that these strategies may be applied to multiple users that eithershare the same food and/or meals. For example, a combined food databasemay be created for a household so that if one member of the house goteggs and another member of the house got milk from the grocery storethat both eggs and milk would be represented in the food database.Similarly, the nutritional preferences (e.g., vegetarian, allergic tocertain foods, etc.), activity, basal metabolic rate, and total calorieburn may be used to form a recommendation on what food/recipe to prepareand/or purchase.

Biometric signals including, but not limited to, heart rate and heartrate variability may provide indications of pre-conditions of diseases.This information may be used to recommend that the user purchase,consume, and/or prepare particular foods so as to reduce their risk ofthe disease(s) for which they have the pre-conditions. For example, if auser has a precondition for cardiac problems, it may be recommended thatthey purchase more vegetables, consume less fatty foods, and preparefood in methods which require less oil (e.g., not deep frying).

Control “Smart Appliance”

In another embodiment, various appliances may all be Wi-Fi enabled, andmay communicate with servers. Since the app (which may be connected tothe appliances via, for example, the cloud or the Internet) may knowwhich food items the refrigerator contains, the app may communicate withthe refrigerator to lower or raise the temperature of the refrigeratordepending on the food items. For example, if many of the food items aremore sensitive to cold, such as vegetables, the refrigerator may beinstructed to raise the temperature. The app may also directlycommunicate with the refrigerator as well via Bluetooth, BTLE, or NFC.

Food Logging

The app may also provide items to log in as the user's food based on agrocery shopping list (which may, for example, be a list maintainedwithin the app) and food recipes that the app recommended. In case ofprecooked meals (e.g., frozen dinner) or produce that does not requireany further processing before being eaten, the user may simply inputtheir serving size (or in the case that the user eats the whole meal,the user may not need to enter a serving size), and then the foodlogging will be completed. Since the grocery list or receipt providesthe exact brand and maker of certain foods, more accurate nutritionalinformation may be logged into the user's account.

When a user logs a food item that is cooked by following a recipesuggested by the app, the app may calculate nutritional information fromthe ingredients and cooking procedure. This may provide more accurateestimate of calorie intake than a simple categorization of the endproduct/meal, since many recipes exist to prepare a particular type offood, e.g., meatballs for pasta may be made with beef, turkey, pork,etc., and may include varying degrees of carbohydrates.

Sport Metric Acquisition Using a Sensor Device

In some embodiments, a sensor may be mounted on a racket, e.g., tennisracket, to help to measure the different strokes of the player. This maybe applicable to most, if not all, racket sports including, but notlimited to, tennis, racquetball, squash, table tennis, badminton,lacrosse, etc., as well as sports played with a bat like baseball,softball, cricket, etc. Similar techniques may also be used to measuredifferent aspects of golf. Such a device can be mounted on the base ofthe racket, on the handle or on the shock absorber typically mounted onthe strings. This device may have various sensors like an accelerometer,gyroscope, magnetometer, strain sensor, and/or microphone. The data fromthese sensors may either be stored locally or transmitted wirelessly toa host system on a smartphone or other wireless receiver.

In some embodiments of a biometric monitoring device, a wrist mountedbiometric monitoring device including an accelerometer, gyroscope,magnetometer, microphone, etc. may perform similar analysis of theuser's game or motions. This biometric monitoring device may take theform of a watch or other band worn on the user's wrist. Racket- orbat-mounted sensors that measure or detect the moment of impact betweenthe bat or racket and the ball and wirelessly transmit such data to thewrist-mounted biometric monitoring device may be used to improveaccuracy of such algorithms by accurately measuring the time of impactwith the ball.

Both wrist and racket-/bat-mounted devices may help measure differentaspects of the user's game including, but not limited to, stroke-type(forehand, backhand, serve, slice, etc.), number of forehands, number ofbackhands, ball spin direction, topspin, service percentage, angularvelocity of racket head, backswing, shot power, shot consistency, etc.The microphone or the strain sensor may be used in addition to theaccelerometer to identify the moment at which the ball impacts theracket/bat. In cricket and baseball, such a device may measure thebackswing, the angular velocity of the bat at the time of impact, thenumber of shots on the off-side vs. leg-side (cricket). It may alsomeasure the number of swings and misses and the number of defensive vs.offensive strokes. Such a device may also have a wireless transmitter totransmit such statistics in real time to a scoreboard or to individualdevices held by spectators.

The wrist- or racket-mounted device may have a small number of buttons(e.g., two) that may be used by the player to indicate when a volley iswon or when an unforced error occurs. This will allow the algorithm tocalculate the fraction of winners and unforced errors that are forehandsvs. backhands. The algorithm may also keep track of the number of acesvs. double-faults in tennis. If both players use such a system, thesystem may also automatically keep track of the score.

Bicycle Handlebar Based ECG

In some embodiments of biometric monitoring devices, a user's heart ratemay be monitored using an electrode in contact with the left hand and anelectrode in contact with the right hand (an ECG heart ratemeasurement). As riding a bicycle requires the user to make hand contactwith either side of the handlebars, this particular activity is wellsuited to tracking user heart rate using ECG techniques. By embeddingelectrodes in the handlebars or handlebar grips or tape, the user'sheart rate may be measured whenever the user is holding the handlebars.For bicycles that have grips (as opposed to using handlebar tape),electrodes may be incorporated into a special grip that may be used toreplace the existing grips, e.g., the factory-installed grips, which aretypically non-conductive. The left and right grips may be electricallyconnected to electronics that measure the ECG signal, using a wire, forexample. In the case that the handlebars themselves are conductive, thehandlebars may be used to electrically connect one of the grips to theelectronics that measure the ECG signal. The electronics that measurethe ECG signal may be incorporated into one or both of the grips.Alternatively, the electronics that measure the ECG signal may belocated in a separate housing. In one embodiment, this separate housingmay be mounted on the bicycle handlebar or stem. It may have functionsand sensors that typical bicycle computers have (e.g., speed sensor,cadence sensor, GPS sensor). It may also have atypical sensors such as awind speed sensor, GSR sensor(s), and accelerometer sensor (potentiallyalso incorporated into the handlebars). This embodiment may usetechniques described in this disclosure to calculate activity metricsincluding, but not limited to, calorie burn, and transmit these metricsto secondary and tertiary device(s) (e.g. smartphones and servers).

Electrodes for the ECG may be incorporated into parts of the bike oraccessories other than into grip tape and handlebar grips such as intogloves, brake hoods, brake levers, or the handlebars themselves. Theseelectrodes or additional electrodes may be used to measure GSR, body fatand hydration in addition to, or in alternative to, heart rate. In oneexample, the user's heart rate may be measured using conductive threads(used as ECG electrodes) sewn into grip tape installed on the handlebar.The grip tape electrodes may be connected to a central bike computerunit that contains electronics to measure GSR, hydration, and/or heartrate. The biometric monitoring device may display this information on adisplay. If the user's hydration or heart rate exceeds a certainthreshold, the user may be alerted to drink more, drink less, increaseintensity or decrease intensity. In the case that the bike computermeasures only one or two of GSR, hydration or heart rate, algorithms maybe used to estimate metrics which that cannot be measured directly. Forexample, if the biometric monitoring device can only measure heart rateand duration of exercise, a combination of heart rate and duration ofexercise may be used to estimate hydration and alert the user when theyshould drink. Similarly, heart rate and exercise duration may be used toalert the user when they should eat or drink something other than water(e.g., a sports drink).

Indirect Metric Estimation

Bicycle computers typically measure a variety of metrics including, butnot limited to, speed, cadence, power, and wind speed. In the case thatthe portable monitoring device does not measure these metrics or is notin communication with devices which may be able to supply these metrics,these and other metrics may be inferred using the sensors that theportable biometric monitoring device does have. In one embodiment, theportable biometric monitoring device may measure heart rate. It may usethis measurement to infer/estimate the amount of power that the user isoutputting. Other metrics such as the user's age, height, and weight mayhelp inform the power measurement. Additional sensor data such asGPS-measured speed, altitude gain/descent, bicycle attitude (so as themeasure the incline or decline of a slope), and accelerometer signalsmay be used to further inform the power estimate. In one embodiment, anapproximately linear relationship between heart rate and power outputmay be used to calculate the user's power output.

In one embodiment, a calibration phase may occur where the user takesdata from the portable biometric monitoring device and a secondarydevice that may be used during calibration as a baseline but not be usedat a later time (e.g., a power meter). This may allow a relationshipbetween sensor data measured by the portable monitoring device andsensor data measured by the secondary device data to be determined. Thisrelationship may then be used when the secondary device is not presentto calculate estimated values of data that is explicitly provided by thesecondary device but not by the biometric monitoring device.

Activity Based Automatic Scheduling

In one embodiment, the day's travel requirements (to work, from work,between meetings) may be scheduled for the user based on the informationin their calendar (or emails or text messages etc.), with the aim ofmeeting daily activity goal(s) or long term activity goal(s). The user'shistorical data may be used to help plan both meeting the goal(s) andalso the transit time required. This feature may be combined withfriends or colleagues. The scheduling may be done such that a user maymeet a friend along the way as they walk to work, or meet a colleague onthe way to a meeting (the user might need to set a rendezvous point,though). If there is real-time communication between biometricmonitoring devices of the user and the user's friend, the user may bedirected to walk a longer route if data from the friend's biometricmonitoring device indicates that their friend is running late.

In another embodiment, walking/running/fitness routes may be suggestedto the user based (in whole or in part) on their proximity to the user.The data for such recommendations could also or additionally be based onGPS info from other users. If there is real-time communication, the usermay be directed to a busy route or a quiet route as preferred. Knowingheart rate and basic fitness information about other users may allow thesystem to suggest a route to match a user's fitness level and thedesired exercise/exertion level. Again this information may be used forplanning/guiding a user to longer term activity/fitness goals.

Location/Context Sensing and Applications

Through one or more methods, embodiments of the biometric monitoringdevices disclosed herein may have sensors that can determine or estimatethe location and or context (e.g. in a bus, at home, in a car) of thebiometric monitoring device. Purpose-built location sensors such as GPS,GLONASS, or other GNSS (Global Navigation Satellite System) sensors maybe used. Alternatively, location may be inferred, estimated or guessedusing less precise sensors. In some embodiments in which it is difficultto know the user's location, user input may aid in the determination oftheir location and or context. For example, if sensor data makes itdifficult to determine if a user was in a car or a bus, the biometricmonitoring device or a portable communication device in communicationwith the biometric monitoring device or a cloud server which is incommunication with the biometric monitoring device may present a queryto the user asking them if they took the bus today or took a car.Similar queries may occur for locations other than vehicular contexts.For example, if sensor data indicate that the user completed a vigorousworkout, but there is no location data that indicates that the user wentto a gym, the user may be asked if they went to the gym today.

Vehicular Transportation Detection

In some embodiments, sensors of the biometric monitoring device and/or aportable electronic device in communication with the biometricmonitoring device and/or a server which communicates with the biometricmonitoring device may be used to determine what type of vehicle (if any)the user is, or was, in. Note that in the embodiments below, a sensor inone or more biometric monitoring devices and/or portable electronicdevices may be used to sense the relevant signal. Also note that whilespecific network protocols such as WiFi or Bluetooth may be used in thefollowing descriptions, one or more alternative protocols such as RFID,NFC, or cellular telephony may also be used.

In one embodiment, the detection of a Bluetooth device associated with avehicle may be used to infer that the user is in a vehicle. For example,a user may have a car that has a Bluetooth multimedia system. When theuser gets close enough to their car for a long enough period of time,the sensor device may recognize the Bluetooth identification of themultimedia system and assume that the user is in the car. Data fromother sensors may be used to corroborate the assumption that the user isin the vehicle. Examples of data or signals from other sensors that maybe used to confirm that the user is in a car include a GPS speedmeasurement that is higher than 30 mph and accelerometer signals thatare characteristic of being in a car. Information intrinsic to theBluetooth ID may be used to determine that it is a Wi-Fi router of avehicle or type of vehicle. For example, the Bluetooth ID of a router ina car may be “Audi In-Car Multimedia.” The keyword “Audi” or “Car” maybe used to guess that the router is associated with a vehicle type of“car.” Alternatively, a database of Bluetooth ID's and their associatedvehicles may be used.

In one embodiment, a database of Bluetooth ID's and their associatedvehicles may be created or updated by the user of a biometric monitoringdevice or through portable communication device data. This may be donewith and/or without the aid of user input. In one embodiment if abiometric monitoring device can determine whether or not it is in avehicle, vehicle type, or specific vehicle without the use of BluetoothID, and it encounters a Bluetooth ID that moves with the vehicle, it maysend the Bluetooth ID and information regarding the vehicle to a centraldatabase to be catalogued as a Bluetooth ID that corresponds with avehicle. Alternatively, if a user inputs information about the vehiclethey are in or were in at a previous point in time and there is aBluetooth ID that was encountered during or close to the time that theuser indicated they were in the vehicle, the Bluetooth ID and vehicleinformation may be sent to a central database and associated with oneanother.

In another embodiment, the detection of a Wi-Fi device associated with avehicle may be used to infer that the user is in that vehicle or type ofvehicle. Some trains, buses, airplanes, cars, and other vehicles haveWi-Fi routers in them. The SSID of the router may be detected and usedto infer or aid an inference that a user is in a specific vehicle ortype of vehicle.

In one embodiment, a database of SSID's and their associated vehiclesmay be created or updated with the user of a biometric monitoring deviceor through portable communication device data. This may be done withand/or without the aid of user input. In one embodiment, if a biometricmonitoring device can determine whether or not it is in a vehicle,vehicle type, or specific vehicle without the use of an SSID, and itencounters an SSID that moves with the vehicle, the biometric monitoringdevice may send the SSID and information regarding the vehicle to acentral database to be catalogued as an SSID that corresponds with avehicle. Alternatively, if a user inputs information about the vehiclethey are in or were in at a previous point in time and there is an SSIDthat was encountered during or close to the time that the user indicatedthey were in the vehicle, the SSID and vehicle information may be sentto a central database and associated with one another.

In another embodiment of a biometric monitoring device, location sensorsmay be used to determine the track of a user. This track may then becompared to a database of routes for different modes of transit. Modesof transit may include, but are not limited to walking, running, biking,driving, taking a bus, taking a train, taking a tram, taking the subway,and/or motorcycling. If the user's track corresponds well with a routeof a specific mode of transit, it may be assumed that the user used thatmode of transit for the period of time that it took them to traverse theroute. Note that the speed with which the route or sections of the routewere completed may improve the guess of the mode of transit. Forexample, a bus and a car may both be able to take the same route, butthe additional stopping of the bus at bus stops may allow the device todetermine that the user was taking a bus rather than a car. Similarly,the discrimination between biking and driving a route may be aided bythe typical difference of speed between the two. This difference inspeed may also depend on the time of day. For example, some routes maybe slower by car during rush hour.

In another embodiment, a biometric monitoring device may be able todetect that the user is in or near a vehicle based on measurements ofthe magnetic field of vehicle. In some embodiments, the magnetic fieldsignature of a location typically associated with the vehicle (e.g.,train station, subway station, bus stop, car garage) may also be used toinfer that the user is currently in, will be, or has been in a vehicle.The magnetic field signature may be time invariant or time varying.

If it is determined that the user was indeed in a vehicle for a periodof time, other metrics about the user may be modified to reflect such astatus. In the case that the biometric monitoring device and/or portableelectronic device can measure activity metrics such as steps taken,distance walked or run, altitude climbed, and/or calories burned, thesemetrics may be modified based on information about vehicular travel. Ifany steps taken or altitude climbed were incorrectly logged during thetime that the user is in a vehicle, they may be removed from the log ofmetrics about the user. Metrics derived from the incorrectly loggedsteps taken or altitude climbed such as distance travelled and caloriesburned may also be removed from the log of metrics about the user. Inthe case that it can be determined in real-time or near real-timewhether or not the user is in a vehicle, the sensors detecting metricswhich should not be measured while in a vehicle (e.g. steps taken,stairs climbed) may be turned off or algorithms which are used tomeasure these metrics may be turned off to prevent incorrectly loggedmetrics (as well to save power). Note that metrics regarding vehicle usesuch as type of vehicle taken, when it was taken, which route was taken,and how long the trip took may be recorded and used later to present theuser with this data and/or to correct other activity and physiologicalmetrics about the user.

Location Sensing Using Bluetooth

Methods similar to those described above may also be used by a biometricmonitoring device to determine when the user comes into proximity ofstatic locations. In one embodiment, Bluetooth ID's from computers(e.g., tablet computers) at restaurants or stores may be used todetermine the user's location. In another embodiment, semi-fixedBluetooth ID's from portable communication devices (e.g., smartphones)may be used to determine a user's location. In the case of semi-fixedBluetooth ID sources, multiple Bluetooth ID's may be need to reach anacceptable level of confidence of the location of the user. For example,a database of Bluetooth ID's of the coworkers of a user may be created.If the user is within range of several of these Bluetooth ID's duringtypical working hours, it may be assumed that the user is at work. Thedetection of other Bluetooth ID's may also be used to record when twousers meet up. For example, it may be determined that a user went for arun with another user by analyzing pedometer data and Bluetooth ID's.Similar such concepts are discussed in further detail in U.S.Provisional Patent Application No. 61/948,468, filed Mar. 5, 2014, andpreviously incorporated by reference with regard to such concepts.

Uncertainty Metric for GPS Based on Location

When fusing sensor signals with GPS signal to estimate informativebiometrics, such as steps, live pace, speed, or trajectory of trips,quality of the GPS signal is often very informative. However, GPS signalquality is known to be time-varying, and one of the factors that affectsthe signal quality is environmental surroundings.

Location information may be used to estimate GPS signal quality. Aserver may store a map of area types, where the area types arepre-determined by number and kind of objects that deteriorate GPSsignals. The types may, for example, be: large building area, smallbuilding area, open area, side-by-water area, and forested area. Thesearea types are then queried when GPS sensor gets turned on with its veryfirst few location estimates, which are expected to be rough andinaccurate. With the rough GPS estimates of the location, possible typesof areas may be returned, and these area types may then be taken intoaccount in the calculation of the GPS signal quality and reliability.

For example, if a user is in or near an urban canyon (an area surroundby tall buildings) such as downtown San Francisco, a low certainty maybe associated with any GNSS location measurements. This certainty may beused later by algorithms that attempt to determine the user's track,speed, and/or elevation based on, at least in part, GPS data.

In one embodiment, a database of location and GPS signal quality may becreated automatically using data from one or more GNSS sensors. This maybe automatically performed by comparing the GNSS tracks with a map ofstreets and seeing when the GNSS sensors show characteristics of a usertravelling along a street (e.g., having a speed of 10 mph or higher),but their track is not located on a road. The database of GPS certaintybased on approximate location may also be inferred from maps showingwhere there are tall buildings, canyons, or dense forests.

Location Sensing Using Vehicular GNSS and/or Dead Reckoning

Many vehicles have integrated GNSS navigation systems. Users of vehiclesthat don't have integrated GNSS navigations systems often buy a GNSSnavigation system for their car that is typically mountednon-permanently in the driver's field of view. In one embodiment, aportable biometric monitoring device may be able to communicate with thevehicle's GNSS system. In the case where the portable biometricmonitoring device is also used to track location, it may receivelocation information from the vehicle GNSS. This may enable thebiometric monitoring device to turn off its own GNSS sensor (in the casethat it has one), therefore reducing its power consumption.

In addition to GNSS location detection, a vehicle may be able totransmit data about its steering wheel orientation and/or itsorientation with respect to the earth's magnetic field in addition toits speed as measured using the tire size and tire rotational velocity.This information may be used to perform dead-reckoning to determine atrack and/or location in the case that the vehicle does not have a GNSSsystem or the vehicle's GNSS system cannot get a reliable locationmeasurement. Dead-reckoning location information may supplement GNSSsensor data from the biometric monitoring device. For example, thebiometric monitoring device may reduce the frequency with which itsamples GNSS data and fill in the gap between GNSS location data withlocations determined through dead reckoning.

Step Counter Data Fusion with Satellite-Based Location Determination

In some implementations of a biometric monitoring device, data fromvarious different sensors may be fused together to provide new insightsas to activities of the wearer of the biometric monitoring device. Forexample, data from an altimeter in the biometric monitoring device maybe combined with step count data obtained by performing peak detectionanalysis on accelerometer data from an accelerometer of the biometricmonitoring device to determine when the wearer of the biometricmonitoring device is, for example, climbing stairs or walking uphill (asopposed to riding an elevator or an escalator or walking across flatground).

In another example of sensor data fusion, data from a step counter suchas that discussed above may be combined with distance measurementsderived from GPS data to provide a refined estimate of total distancetraveled within a given window. For example, GPS-based distance or speeddata may be combined with step-counter-based distance or speed (usingsteps taken multiplied by stride length, for example) using a Kalmanfilter in order to obtain a refined distance estimate that may be moreaccurate than either the GPS-based distance or speed measurement or thestep-counter-based distance or speed measurement alone. In anotherimplementation, a GPS-based distance measurement may be filtered using asmoothing constant that is a function of the step rate as measured by,for example, an accelerometer. Such implementations are discussedfurther in U.S. Provisional Patent Application No. 61/973,614, filedApr. 1, 2014, which was previously incorporated herein by reference inthe “Cross-Reference to Related Applications” section and which is againhereby incorporated by reference with respect to content directed atdistance or speed estimation refinement using data from satellite-basedlocation systems and step count sensors.

Biometric and Environmental/Exercise Performance Correlation

Some embodiments of portable monitoring devices described herein maydetect a variety of data including biometric data, environmental data,and activity data. All of this data may be analyzed or presented to auser to facilitate analysis of or correlation between two or more typesof data. In one embodiment, a user's heart rate may be correlated to carspeed, biking speed, running speed, swimming speed or walking speed. Forexample, the user may be presented with a graph that plots biking speedon the X axis and heart rate on the Y axis. In another example, a user'sheart rate may be correlated to music that they were listening to. Thebiometric monitoring device may receive data regarding what music theuser was listening to through a wireless connection (e.g., Bluetooth) toa car radio. In another embodiment, the biometric monitoring device mayalso function as a music player itself, and therefore can record whichsong was played when.

Weight Lifting Aid

Without the aid of a personal trainer or partner, it may be difficult todo a weight-lifting routine properly. A portable biometric monitoringdevice may aid a user in completing a weight lifting routine bycommunicating to the user how long they should hold up each weight, howquickly they should lift it, how quickly they should lower it, and howmany repetitions of each lift to perform. The biometric monitoringdevice may measure the user's muscle contractions using one or more EMGsensors or strain sensors. The user's muscle contractions may also beinferred by measuring vibrations of one or more body parts (for exampleusing an accelerometer), sweat (e.g., using a GSR sensor), rotation ofone or multiple body parts (e.g., using a gyroscope), and/or atemperature sensor on one or more body parts. Alternatively, a sensormay be placed on the weight lifting apparatus itself to determine whenthe using is lifting, with how much speed they are lifting or lowering,how long they are lifting for, and how many repetitions of lifts theyhave performed.

In one embodiment, if the biometric monitoring device or weight liftingapparatus detects that the user is approaching their failure limit (whenthe user can no longer support the weight), the weight lifting apparatusmay automatically lift the weight or prevent the weight from beinglowered. In another embodiment, a robot in communication with thebiometric monitoring device or weight lifting apparatus mayautomatically lift the weight or prevent the weight from being lowered.This may allow the user to push themselves to their limit withoutneeding a partner/spotter (to lift the weight in case of failure) andwithout risking injury from dropping the weight.

Glucose Level Monitoring Aid

In some embodiments, a portable biometric monitoring device may beconfigured to aid users who need to monitor their glucose levels (e.g.,diabetics). In one embodiment, the portable biometric monitoring devicemay indirectly infer a user's glucose level or a metric related to theuser's glucose level. Sensors other than those typically used inmonitoring glucose monitoring (using continuous or discrete finger-pricktypes of sensors) may be used in addition to, as an alternative to, oras an aid to the typical glucose monitoring methods. For example, anbiometric monitoring device may alert the user that they should checktheir blood glucose level based on data measured from sensors on thebiometric monitoring device. If the user has performed a certain type ofactivity for a certain amount of time, their blood glucose level islikely to have decreased, and therefore, the biometric monitoring devicemay display an alert, create an auditory alert, or vibrate to alert theuser that their blood glucose may be low and that they should check itusing a typical glucose measurement device (e.g., a finger-prick typeglucose monitor). The biometric monitoring device may allow the user toinput the glucose level that is measured from the glucose meter.Alternatively, the glucose measurement may be automatically transmittedto the biometric monitoring device and/or a third device in direct orindirect communication with the biometric monitoring device (e.g., asmart phone or server). This glucose measurement may be used to informthe algorithm used by the biometric monitoring device to determine whenthe next glucose level alert should be delivered to the user. The usermay also be able to enter what food they ate, are eating, or areplanning to eat into the biometric monitoring device or a device indirect or indirect communication with the biometric monitoring device.This information may also be used to determine when the user should bealerted to check their blood glucose level. Other metrics and sensordata described herein (e.g., heart rate data) may also be used alone orin combination to determine when the user should be alerted to checktheir blood glucose.

In addition to being alerted when glucose levels should be checked, abiometric monitoring device may also display an estimate of the currentglucose level. In another embodiment, data from the biometric monitoringdevice may be used by a secondary device (e.g., a smart phone or server)to estimate the user's glucose level and/or present this data to theuser (e.g., by displaying it on a smartphone, on a webpage, and/or bycommunicating the data through audio).

A biometric monitoring device may also be used to correlate exercise,diet, and other factors to blood glucose level. This may aid users inseeing the positive or negative effects of these factors on their bloodglucose levels. The blood glucose levels with which the activity iscorrelated to may be measured by the user using a different device(e.g., a finger-prick monitor or continuous blood glucose monitor), bythe biometric monitoring device itself, and/or by inferring the bloodglucose level or a metric related to the glucose level using othersensors. In some embodiments of biometric monitoring devices, a user maywear a continuous glucose monitoring device and a biometric monitoringdevice. These two devices may automatically upload data regardingactivities and glucose levels to a third computing device (e.g., aserver). The server may then analyze the data and/or present the data tothe user so that they become more aware of the relationship betweentheir activities and glucose levels. The server may also receive inputon the user's diet (e.g., the user may enter what foods they eat) andcorrelate the diet with glucose levels. By helping the user understandhow diet, exercise, and other factors (e.g., stress) affects their bloodglucose levels, biometric monitoring devices may aid users who havediabetes.

UV Exposure detection

In one embodiment, the biometric monitoring device may have the abilityto monitor an individual's exposure to UV radiation. UVA and UVB may bemeasured with one or multiple sensors. For example, a photodiode havinga bandpass filter which passes only UVA may detect UVA exposure and aphotodiode having a bandpass filter which passes only UVB may detect UVBexposure. The user's skin pigmentation may also be measured using acamera or reflectometer (light emitter and light detector whichdetermines the efficiency with which light is reflected off the skin).Using UVA, UVB, and skin pigmentation data, the biometric monitoringdevice may provide a user with information regarding the amount of UVexposure they have been subjected to. The biometric monitoring devicemay also provide estimates or alarms regarding over exposure to UV,potential for sunburn, and potential for increasing their risk of skincancer.

Screen Power Saving Using User Presence Sensors

The portable biometric monitoring device may have one or more a displaysto present information to the user. In one embodiment sensors on thebiometric monitoring device may determine the user is using thebiometric monitoring device and/or wearing the biometric monitoringdevice to determine the state of the display. For example, a biometricmonitoring device having a PPG sensor may use the PPG sensor as aproximity sensor to determine when the user is wearing the biometricmonitoring device. If the user is wearing the biometric monitoringdevice, the state of the screen (e.g. a color LCD screen) may be changedto “on” or “standby” from its typical state of being off.

Power Conservation with Respect to Satellite-Based LocationDetermination Systems

In some implementations, certain systems included in a biometricmonitoring device may consume relatively large amounts of power comparedto other systems in the biometric monitoring device. Due to the smallspace constraints of many biometric monitoring devices, this mayseriously affect overall battery charge life for the biometricmonitoring device. For example, in some biometric monitoring devices, asatellite-based location determination system may be included. Each timethe satellite-based location determination system is used to obtain aposition fix using data from the GPS satellite constellation, it usespower drawn from the biometric monitoring device battery. The biometricmonitoring device may be configured to alter the frequency with whichthe satellite-based location determination system obtains a location fixbased on data from one or more sensors of the biometric monitoringdevice. This adaptive location fix frequency functionality may helpconserve power while still allowing the satellite-based locationdetermination system to provide location fixes at useful intervals (whenappropriate).

For example, if a biometric monitoring device has an ambient lightsensor, data from the ambient light sensor may be used to determinewhether the lighting conditions indicate that the biometric monitoringdevice is likely indoors as opposed to outdoors. If indoors, thebiometric monitoring device may cause the location fix frequency to beset to a level that is lower than the location fix frequency that may beused when the lighting conditions appear to indicate that the biometricmonitoring device is outdoors. This has the effect of decreasing thenumber of location fixes that are attempted when the biometricmonitoring device is indoors and thus less likely to obtain a goodlocation fix using a satellite-based location determination system.

In another example, if motion sensors of the biometric monitoring deviceindicate that the wearer of the biometric monitoring device issubstantially stationary, e.g., sleeping or generally not moving morethan a few feet every minute, the location fix frequency of thesatellite-based location determination system may be set to a lowerlevel than if the motion sensors indicate that the wearer of thebiometric monitoring device is in motion, e.g., walking or running fromone location to another, e.g., moving more than a few feet.

In yet another example, the biometric monitoring device may beconfigured to determine if the biometric monitoring device is actuallybeing worn by a person—if not, the biometric monitoring device may setthe location fix frequency to a lower level than if the biometricmonitoring device is actually being worn. Such determinations regardingwhether or not the biometric monitoring device is being worn may bemade, for example, when motion data collected from motion sensors of thebiometric monitoring device indicate that the biometric monitoringdevice is substantially immobile, e.g., not even demonstrating smallmovements experienced by biometric monitoring devices when the wearer issleeping or sedentary, or when data, for example, from a heart ratesensor indicates that no heart rate is detected. For optical heart ratesensors, if there is little or no change in the amount of light detectedby the light detection sensor when the light source is turned on andoff, this may be indicative of the fact that the heart rate sensor isnot pressed against a person's skin and that, by inference, thebiometric monitoring device is not being worn. Such adaptivesatellite-based location determination system fix frequency concepts arediscussed in more detail in U.S. Provisional Patent Application No.61/955,045, filed Mar. 18, 2014, which was previously incorporatedherein by reference in the “Cross-Reference to Related Applications”section and which is again hereby incorporated by reference with respectto content directed at power conservation in the context ofsatellite-based location determination systems.

It is to be understood that biometric monitoring devices, in addition toincluding the features discussed below in more detail, may also includeone or more features or functionalities discussed above or discussed inthe various applications incorporated by reference in the abovediscussion. Such implementations are to be understood as being withinthe scope of this disclosure.

While the above discussion has focused on a variety of different systemsand functionality that may be included in a biometric monitoring device,the discussion that follows below focuses on some particular embodiments(some of which may also be discussed above) in further detail.

Heart Rate Monitor with Automatic Detection of Unworn and Worn States

Some embodiments provide methods for operating a heart rate monitor of awearable fitness monitoring device to measure one or morecharacteristics of a heartbeat waveform. A “heartbeat waveform” as usedherein refers to a variation of any measured signal caused by orcorrelated with a user's heartbeat driven blood flow. In someembodiments, the measured signal relates to blood circulation caused bythe heart pumping blood through the circulatory system, which causescardiovascular driven variations in capillary volume or other parameter.In some embodiments, the heartbeat waveform is measured byphotoplethysmography (PPG). In such embodiments, the heartbeat waveformreflects blood volume changes in capillaries, which correlates with auser's heartbeat and pulse (an arterial palpation caused by theheartbeat). In some embodiments, the measured signal relates to muscularactivities of the heart or electrocardiographic signals. In someembodiments, the cardiac activities or signals can be measured by ECG toobtain the heartbeat waveform.

A heartbeat waveform represents information for one or more cardiaccycles, which corresponds to a complete heartbeat from its generation tothe beginning of the next beat. The frequency of the cardiac cycle isdescribed by the heart rate, which is typically expressed as beats perminute. A heartbeat waveform typically includes information aboutvarious stages of a heartbeat, e.g., amplitude, frequency, and/or shapeof waveform over one or more cardiac cycles. In many embodiments, aheartbeat waveform is used to obtain a user's heart rate.

In some embodiments, optical heart rate monitors may be used in thewearable device, implementing different modes of operation by emittingpulses of light and detecting light after it interacts with the user'sskin or other tissue, to thereby capture data that may be used to obtainthe user's heartbeat waveform, worn state, user characteristics, etc.

In some embodiments, the current disclosure provides methods foroperating a wearable fitness monitoring device having a heart ratemonitor (HRM) in a low power state when the device determines that thedevice is not worn by a user, or is “off-wrist” when implemented in awrist-worn device. This feature of the HRM is also referred to as an“automatic off” function. In some embodiments, the automatic offfunction is implemented by operating the HRM in an “unworn” (or“off-wrist”) detection mode, and the automatic off functionautomatically turns off the heart rate monitoring operations of the HRMto conserve energy if the device determines that it is not being worn bythe user. Other benefits of the automatic off function include providingmore accurate heart rate estimation. For example, when an automatic offor automatic on (described below) is performed a heart rate detectionalgorithm may reset. In one implementation, the algorithm stops runningwhen off-wrist is detected, and restarts when on-wrist is detected. Whenthe heart rate monitor restarts, it resets.

In some embodiments, the current disclosure provides methods foroperating a wearable fitness monitoring device having a heart ratemonitor in a normal power state when the device is worn by the user, or“on-wrist” when implemented in a wrist-worn device. This feature of theHRM is also referred to as an “automatic on” function. In someembodiments, the automatic on function is implemented by operating theHRM in a “worn” (or “on-wrist”) detection mode. The automatic onfunction automatically takes the HRM out of a low power state and turnson the heart rate monitoring operations of the HRM if the device detectsmotion and determines that it is worn by the user.

In some embodiments, the unworn (or off-wrist) and worn (or on-wrist)detection may be implemented by light (e.g., LED) probing, which emitslight pulses and detects signals after the light pulses interact withthe user's skin and tissues. In some embodiments, the unworn and wornprobing may share some hardware, firmware, software, and/or parametersfor light emission, light detection, and analyses of detected signals.In other embodiments, the two probing modes employ different hardware,firmware, software, and/or parameters for light emission, lightdetection, and analyses may be used for unworn and worn detection.

In some embodiments, the wearable fitness monitoring device goes in andout of the low power state regulated by a probe light (e.g., LED) and amotion detector, implementing automatic off and on functions. In the lowpower state, the heart rate monitor saves power by turning off, orscaling back operation of, its LED light source and its photodetector.In some embodiments, other light sources and light detectors (e.g.,photodiodes, photomultiplier tubes, CCD, or CMOS) may be used toimplement the automatic off and on functions. FIG. 17A shows such animplementation, where in the same probe light mechanism is used todetermine whether the heart rate monitor is worn (“on-wrist”) or unworn(“off-wrist”). In other embodiments described below, two different probelight mechanisms may be used to determine the on-wrist state and theoff-wrist state of the monitor. As one skilled in the art willrecognize, although the heart rate monitors described herein aredescribed as being worn on the wrist of the user, other types ofimplementation may allow the user to wear the heart rate monitor inalternative fashions, such as on the ankle or the chest of the user. Insuch implementations, the worn state and unworn state respectivelycorrespond to the “on-wrist state” and “off-wrist” state of theimplementations described below.

As shown in FIG. 17A, an LED or another light source emits pulses oflight that can be detected by a photodetector of the heart rate monitorof a wearable fitness monitoring device (also referred to as a wearabledevice). Typically when the device is worn by the user, the emittedlight will interact with the skin and/or other tissue of the user, andthen be detected by the photodetector of the heart rate monitor. If thedevice is not worn by the user, the emitted light will not be detectedby the photodetector, or will be detected with a different intensity orpattern. The difference in detected light provides data that the heartrate monitor may analyze to determine whether the device is being wornby the user on not. See block 1702. In the implementations depictedhere, as the wearable fitness monitoring device determines that it isworn on the wrist, it maintains in the operational mode of lightprobing. If the heart monitor determines that the wearable device is notworn by the user, e.g., an off-wrist state is detected, the heart ratemonitor switches into a low power state where it does not emit or detectlight pulses, thereby saving electricity for the wearable device. Seeblock 1704. In the implementation depicted here, the wearable device mayremain in the low power state or return to the light probing state,which may be regulated by the user's motion. In the implementationdepicted here, if the heart rate monitor is in a low power state, itremains in such a state if no motion is detected. However, it returns tothe light probing state when motion is detected indicating that the useris likely wearing the wearable fitness monitoring device. This motionregulated low power state avoids the need to use a light source andlight detector to regulate the heart rate monitor, enabling furtherpower saving. Motion detection for worn detection mode may beimplemented by any one of the motion detectors suitable for a wearabledevice as described above. For instance, the motion detection may beimplemented by an algorithm detecting stillness or motion from datagenerated by a motion sensor. Another example can use a motion sensor'sinnate interrupt for waking up the sensor, which can trigger the worndetection.

In the implementation depicted in FIG. 17A, the heart rate monitor maymeasure heart rate or other heartbeat waveform related signalsconcurrently when it performs the light probing function depicted byblock 1702. The depicted light probing mechanism of 1702 determineswhether the heart rate monitor should remain in the light probing modeand continue performing the heart monitoring function. The same lightprobing mechanism also determines whether the heart rate monitor shouldexit light probing and heart rate monitoring. As shown in FIG. 17B,separate light probing mechanisms may be used for off-wrist detection toexit PPG heart rate monitoring and for on-wrist detection to enter PPGheart rate monitoring.

In some embodiments, the light probing mode for detecting “on-wrist”state, as depicted in block 1708 of FIG. 17B, may emit light pulses in arelatively low intensity for a percentage of time. If the light emittedby the light source interacts with the user's skin or other tissues, thereflected or scattered light will be detected by the photodetector ofthe heart rate monitor. When this occurs, the heart rate monitor entersa normal power state as depicted by block 1706. When this does notoccur, the heart rate monitor continues light probing for a particulartime period. If a specific time period has elapsed and no userinteraction is detected by the light probing, the wearable device entersa low power state as depicted in Block 1710.

The heart rate monitor in the normal power state performs both a heartrate monitoring function and a worn detection probing function, as shownin Block 1706. The light probing mechanism for unworn detection of block1706 can operate at relatively high power compared to that ofworn-detection in block 1708 in some embodiments. In some embodiments,the function of 1708 is implemented in two states: one when entered fromthe off-wrist state and a different function when entered from theon-wrist state. This embodiment will be described in more detail below.In other embodiments, similar light pulses may be used for detectingtransitions to unworn and for detecting transitions to worn. In someembodiments, different analyses may be applied to unworn detection orworn detection. For instance, unworn detection may be triggered byspecific intensity variation pattern of detected light pulses, whileworn detection may be triggered by intensity of detected light pulses.Examples of emission and detection of light pulses for unworn/worndetection are further described below.

The light probing mechanism of 1706 may determine whether the BMD isoff-wrist (or unworn). If not, it remains in the normal power state toperform heart signal monitoring. If off-wrist state is detected, itstops PPG heart rate monitoring, exiting normal power mode and returningto the light probing mode of block 1708. After the wearable device hasbeen in light probing mode of 1708 for a particular period withoutdetecting being worn, the wearable device enters the lower power stateof block 1710. The wearable device remains in the lower power state ifno user motion is detected. It returns to the light probing state of1708 if user motion is detected.

FIG. 18A shows a process flow chart according to some embodiments of thedisclosure, where a wearable fitness monitoring device having the heartrate monitor operates in different modes in energy efficient ways. Invarious embodiments as further described below, the heart rate monitoroperates in different modes by emitting light pulses using a lightsource such as one or more LEDs, and detecting light after it interactswith the user's skin or other tissue. The characteristics of the emittedand detected light pulses are further described hereinafter.

In the embodiment depicted here, the wearable fitness monitoring devicestarts by detecting motion of the device. If no motion is detected, thedevice remains in the motion detection mode. See block 1802. If thedevice detects motion it begins operating the heart rate monitor in a“worn detection mode” that is configured to detect the device hastransitioned from an unworn to a worn state. The operation in the secondmode may include pulsing light by a light source (e.g., an LED) anddetecting the light after it interacts with the user's skin and/ortissues. See block 1804. Within a defined time after entering the secondmode, the device determines whether the heart rate monitor detects thatthe device has transitioned to a worn state. See block 1806. If not, thedevice ends the worn detection mode, see block 1807, and returns to themotion detection operation of block 1802. If the device detects atransition to a worn state, it begins operating the heart rate monitorin a first mode that is configured to measure heartbeat waveform orother heart related signals of the user. See block 1808.

The second mode of block 1804 corresponds to a worn detection mode asdescribed elsewhere herein. In one implementation of FIG. 18A, the worndetection mode can be implemented the same way as a second modeconfigured to detect transition to unworn state as shown in block 1810.An alternative embodiment described below related to FIG. 18B implementsworn detection mode and unworn detection mode as two different modes.

As the heart rate monitor operates in the first mode of block 1808, itdetects pulses of light that interact with the user's tissue, capturingsignal variation caused by heartbeat related blood flow in the capillaryvessels of the user. In some embodiments, the heart rate monitor canmeasure other information related to heartbeat waveform as describedabove. Meanwhile, the device periodically and temporarily operate theheart rate monitor in the second mode to detect that the device hastransitioned from a worn state to an unworn state, while also operatingin the first mode to detect heart rate. See block 1810. As the heartrate monitor operates in the second mode, the device determines whetherthe device has transitioned to an unworn state, see block 1812. If not,it continues to operate in both the first mode and the second mode asdepicted in block 1810. If yes, the device ends the first mode formonitoring heartbeat waveform signal. See block 1814. At this point, thedevice returns the heart rate monitor to operate in the motion detectionmode of block 1802.

FIG. 18B shows a process flow chart according to some embodiments of thedisclosure. The process of FIG. 18B is similar to that of FIG. 18A, butpresented with a slightly different focus, starting with concurrentoperation of a first mode for detecting heart signals and a second modefor detecting an unworn state. See block 1822, which may correspond toblock 1810 of FIG. 18A. The process of FIG. 18B implements two differentmodes for unworn detection to automatically turn off heart ratemonitoring (see the second mode in block 1822) and worn detection toturn on heart rate monitoring (see the worn detection mode in block1832). In some implementations, the process of FIG. 18A may use the samemechanism to detect proximity of user's body to turn on (see the worndetection mode of block 1804) and off the heart rate monitoring (see thesecond mode of block 1810).

In the process shown in FIG. 18B, the wearable device operates the heartrate monitor in a first mode to detect heart rate or other heartbeatwaveform characteristics. Concurrently, the heart rate monitor operatesin a second mode to detect user proximity. See block 1822. In theembodiments depicted here, the second mode is implemented to determinewhether the heart rate monitor has transitioned to an unworn (oroff-wrist) state. See block 1824. If the device has not transitioned toan unworn state, the device continues to operate the heart rate monitorin both the first mode and the second mode in the operation of block1822. If the second mode determines that the heart rate monitor isunworn, the device automatically stops the heart rate monitor operationin the first mode. See block 1826. This operation helps to conserveenergy by automatically turning off the heart rate monitor when thedevice is not worn by the user. In some embodiments, the device enters alow-power state that does not monitor heart rate or probe user proximity(also stopping the second mode operation to further conserve energy, notshown in the flowchart).

In the process depicted in FIG. 18B, the wearable device performs motiondetection after stopping the first mode of heart signal monitoring, themotion detection providing a trigger for automatically turning on theheart rate monitoring function when necessary. See block 1828. Asmentioned elsewhere herein, the motion detection may be implemented bydifferent hardware and software. If no motion is detected, the deviceremains in a low-power state. See block 1830. If motion is detected,which indicates a possibility that the user is interacting with thedevice, the device starts operating in a worn detection mode that isdesigned to determine whether the device is likely worn by the user. Seeblock 1832. If the worn detection mode of the heart rate monitordetermines that it is not worn, the device returns to the motiondetection mode. However, if the heart rate monitor determines that thedevice is worn by the user, the device returns to the operation of block1822 to concurrently operate the heart rate monitor in the first mode todetect heartbeat and in the second mode to detect user proximity(transition to an unworn state). See block 1834. It should be understoodthat while the description of FIGS. 18A and 18B present starting andending points for the device operations, the process may be implementedcontinuously and can start and end at any point in the disclosed flowcharts. In some implementations, the starting and ending points areentered when the user manually turns the device on and off.

As mentioned above, the heart rate monitor of the wearable deviceincludes an optical heart rate monitor in some embodiments. While theheart rate monitor operates in different modes, all modes involveemitting light pulses and detecting the same pulses after they interactwith the user's tissues. The different modes may employ different lightpulses and/or different processes for interpreting detected pulses. FIG.18C shows a cartoon of light pulses that are used to provide data forheart rate vs. the light pulses for probing proximity of the user's bodyin some embodiments. As in the shown embodiments, the heart rate monitoremits light pulses for both a heart rate data stream and a probing datastream. The heart rate data stream as depicted in this embodiment has alower frequency, e.g., of 25 Hz (or 40 ms between two consecutivepulses), while the probing stream has a higher frequency, e.g., of 100Hz (or 10 ms between two consecutive pulses). One skilled in the artappreciates that different frequencies and amplitudes may be used forthe two data streams, while keeping the two data streams separable. Incertain embodiments, the higher frequency is about 2 to 5 times greaterthan the lower frequency, or about 2 to 4 times greater. The twodifferent frequencies of the light pulses allow the heart rate monitorto emit and detect two different signals simultaneously. The heart ratedata stream allows the heart rate monitor to determine the heart ratesignal of the user. The probing data stream allows the heart ratemonitor to determine whether or not the device is in near proximity tothe user's body. In some embodiments, the heart rate data stream mayoperate continuously in a first mode, while the probing stream operatesperiodically in a second mode. For instance, the probing data stream mayoperate for 120 ms every 1000 ms (one second). In some embodiments, theheart rate monitor operates the probing stream for less than about 50%of the time when it operates the heart rate data stream. In otherembodiments, that percentage may be less than about 40%, 30%, 20%, 10%,or 5%.

In some embodiments, as shown in the example here, the heart rate datastream and the probing data stream are in phase, such that some pulsesfrom one stream coincide with some pulses in another stream. Thisarrangement may help to reduce the number of pulses of light, therebysaving energy. In other embodiments, as shown in the following examples,two data streams are off phase, which may provide data streams that aremore readily separable.

FIG. 18D shows another cartoon of light pulses that can be used toprovide data for heart rate vs. the light pulses for probing proximityof the user's body in some embodiments. The light pulses for heart ratedata stream depicted here is similar to that in FIG. 18C. However theprobing data stream here has variable intensity, while the probing datastream in FIG. 18C has fixed intensity. The probing data stream shownhere may also be used to detect user skin characteristics in someembodiments as further described in the next section. In the exampleshown here, the probing data stream includes 8 pulses at 100 Hz, amongwhich four have variable intensities. In some embodiments not shownhere, fewer pulses may have variable intensities, e.g., only two pulseshave variable intensities. In some embodiments, even one pulse may besufficient for probing. In this example, two of the pulses haverelatively low intensities and are different from each other. Forinstance, they may have values of about 0.02 to 0.04 mW for the lowerintensity pulse and about 0.025 to 0.05 mW for the higher intensitypulse. The difference between the two pulses is indicated as D1 in thefigure and may be in the neighborhood of about 0.002 to 0.005 mW. Two ofthe pulses have relatively high intensities and are different from eachother. For instance, they can have values of about 0.1 to 0.11 mW forthe lower intensity pulse and about 0.14 to 0.15 mw for the higherintensity pulse. In other embodiments, the intensity values may beadjusted. As an additional example, a lower intensity pair of pulses mayhave intensities in mW of about 0.01 to 0.03 (e.g., about 0.021) and0.025 to 0.035 (e.g., about 0.027), while a higher intensity pair mayhave pulse intensities of about 0.15 to 0.17 (e.g., about 0.16) andabout 0.17 to 0.19 (e.g., about 0.175).

The difference between the two high intensity pulses is indicated as D2.The difference between the two pairs is labeled as D3. Additionally,four of the eight pulses have an intermediate and constant intensity.The specific numbers and intensities for the different pulses may beadjusted to provide good signal to be measured and analyzed. In someembodiments, the values of D1 and D2 are set to allow detection of adifferent response by the photodetector, which in turn allows analysisof light-user interaction, and user skin characteristics. The lower andhigher intensities and the value of D3 are set to allow capturing lightreflection in a range of likely conditions when the user is wearing thedevice: different skin colors, motions, sweat levels and compositions,ambient light conditions, etc. The intermediate intensity is set toallow capturing of baseline signal. In some embodiments, for instance,the lower intensity pulses provide good detection intensity for lightcolored skins; the high intensity pulses provide good detection for darkcolored skins; and the intermediate intensity pulses provide gooddefault values for baseline detection.

In some embodiments, the intensity of the light measured for any of thepulses may be used to determine worn and/or unworn state, as well asuser skin characteristics. If the user is wearing the device and thelight pulses interact with the user and then are detected, the devicemay infer the user's proximity from the intensity of the detectedsignal. For instance, if the device is worn, the detected intensity maybe higher than unworn, or vice versa. Also, if the device is worn, apulsing frequency consistent with the emitted pulses may be detected. Ifthe device is worn, the difference of detected intensities between apair of pulses can correlate with the difference in the emitted pulses(e.g., D1, D2, or D3). Such differences can provide an inference thatthe device is worn. In some embodiments, a detected difference betweentwo pulses (e.g., the D1 pair) may be normalized by the differencebetween two constant pulses, then the normalized difference may becompared to a threshold value to determine if the device is worn. Thisanalysis helps to eliminate inherent noise in detected light. In otherimplementations, the device determines the variance of the responses.When the variance is high, the device concludes that it is worn, andwhen the variance is low, the device concludes that it is not worn. Insome embodiments further described in the next section, the slope and ortrend of data points of emitted light value (e.g. intensity or power)vs. detected light may be used to obtain user skin responsecharacteristics, which may then be used to calibrate emission powerand/or gain of detection. In some embodiments, the device may have boththe worn/unworn detection function and the skin characteristiccalibration function as further described in the next section.

Some embodiments provide a method of operating a heart rate monitor of awearable fitness monitoring device having a plurality of sensors. Themethod includes: (a) operating the heart rate monitor in a first modewhile also operating in a second mode configured to detect nearproximity of the wearable fitness monitoring device to a user's skin,where the first mode is configured to determine one or morecharacteristics of a user's heartbeat waveform when the wearable fitnessmonitoring device is in near proximity to the user; (b) from informationcollected in the second mode, determining that the heart rate monitor isnot proximate to the user's skin; and (c) in response to determiningthat the heart rate monitor is not proximate to the user's skin, endingoperating the heart rate monitor in the first mode. In some embodiments,the one or more characteristics of the user's heartbeat waveform includethe user's heart rate.

In some embodiments, the wearable device includes a motion sensor, andthe method further involving: prior to (c), determining from informationoutput by the motion detecting sensor that the wearable fitnessmonitoring device has had been still for at least a defined period; andin response to detecting that the wearable fitness monitoring device hashad been still for at least the defined period, performing (c). In someembodiments, prior to (a) while the first mode is not operating, thedevice (i) detects motion of the wearable fitness monitoring deviceusing a motion detecting sensor and/or detecting proximity of the heartrate monitor to the user' skin by operating the heart rate monitor in athird mode; and (ii) initiates operation of the first mode of the heartrate monitor when the wearable fitness monitoring device is determinedto be in near proximity to the user.

In some embodiments, the heart rate monitor operates in the second modeno more than about 50% of the time. In other embodiments, the percentageis no more than about 40%, 30%, 20%, or 10%.

In some embodiments, operating the heart rate monitor in the second modeinvolves pulsing a light source in the heart rate monitor at a secondmode frequency and detecting light from the light source at the secondmode frequency; and operating the heart rate monitor in the first modeinvolves pulsing the light source in the heart rate monitor at a firstmode frequency and detecting light from the light source at the firstmode frequency. In some embodiments, operating the heart rate monitor inthe second mode involves emitting a succession of light pulses ofvariable intensity and determining whether detected light correspondingto the succession of light pulses has a variable response correspondingto the variable intensity of the emitted light pulses.

Some embodiments provide a method of operating a heart rate monitor of awearable fitness monitoring device having a plurality of sensors. Themethod includes: (a) detecting motion of the wearable fitness monitoringdevice using the motion detecting sensor; (b) in response to detectingthe motion in (a), operating the heart rate monitor in a worn detectionmode configured to detect near proximity of the wearable fitnessmonitoring device to a user's skin; and (c) upon determining via theworn detection mode that the wearable fitness monitoring device isproximate to the user's skin, operating the heart rate monitor in afirst mode configured to determine one or more characteristics of theuser's heartbeat waveform. In some embodiments, (a) is performed whenthe heart rate monitor is not operating or is operating in a low powermode. In some embodiments, the method involves, prior to (a): (i)operating the heart rate monitor in the first mode while also operatingin a second mode configured to detect near proximity of the wearablefitness monitoring device to a user's skin; (ii) from informationcollected in the second mode, determining that the heart rate monitor isnot proximate to the user's skin; and (iii) in response to determiningthat the heart rate monitor is not proximate to the user's skin, endingoperating the heart rate monitor in the first mode.

In some embodiments, the heart rate monitor operates in the worndetection mode no more than about 50% of the time. In other embodiments,the percentage is no more than about 40%, 30%, 20%, or 10%.

In some embodiments, operating the heart rate monitor in the worndetection mode includes: emitting light pulses from a light source inthe heart rate monitor having a second frequency and/or phase; detectinglight from the light source at the second frequency and/or phase; anddetermining whether the light detected at the second frequency and/orphase has an intensity and/or pattern indicating that the light from thelight source has interacted with the user's skin. In some embodiments,the emitted light pulses have variable intensity. In some embodiments,the emitted light pulses include a succession of light pulses havingvariable intensity. In some embodiments, a first one of the successionof light pulses has an intensity at least 5 times greater than a secondone of the succession of light pulses. In some embodiments, lowerintensity pulses are emitted at about 0.05 to 0.5 mW (e.g., about 0.012mW) and higher intensity pulses are emitted at about 0.5 to 2 mW (e.g.,about 1.19 mW). In other embodiments, intensities may be adjustedaccording to applications and implementations. In some embodiments, thesuccession of light pulses include a first set of pulses having anintensity providing variable response when interacting with light skin,and where the succession of light pulses includes a second set of pulseshaving an intensity providing a variable response when interacting withdark skin.

Heart Rate Monitor with Automatic Calibration

In some embodiments, the disclosure provide methods and devices toaccurately measure heartbeat waveform for different usercharacteristics, such as skin colors, motion, sweat, position, andphysiologic state (e.g., skin thickness, body fat, etc.) of the users.FIG. 19A shows two relationships between light intensity emitted by alight source of the heart rate monitor vs. the signal detected by thephotodetector. Because darker skin has lower reflectance of light, therelations between photodetector reading and light pulse intensity, e.g.,DAC, tends to have a lower slope than for paler skin. FIG. 19B depictsthe temporal modulation of the TIA signal, where the pattern of themodulation reflects heart beats that modulate the reflection andrefraction of the capillary system of the user. In some embodiments, thesignals for skin characterization may operate intermittently at higherfrequency than the light pulses of the first mode for heart ratemonitoring.

FIG. 19C shows flowchart for a process of operating a heart rate monitorof a wearable fitness monitoring device by adjusting light emissionpower and/or light detection gain of the heart rate monitor. In variousembodiments, the adjustments may be implemented by software, firmware orhardware. The process starts by emitting and detecting light pulses inthe skin characterization mode. See block 1902. In some embodiments, thelight pulses used in the skin characterization mode may be similar oridentical to those for worn and/or unworn detection modes as shown inFIG. 18D. In other embodiments, the light pulses used in the skincharacterization mode may have ramping intensities as shown in FIG. 19D.In some embodiments, the light pulses for the skin characterization modeare in phase with the light pulses for the first mode configured tomeasure heartbeat waveform information. In other embodiments, the lightpulses for the skin characterization mode and the pulses for the firstmode are out of phase as shown in FIG. 19D. FIG. 19D shows light pulsesignal patterns that may be used to regulate a heart rate monitor'slight source intensity and/or light detection gain so as to accuratelymeasure heart rate signals for users with different characteristics suchas skin colors.

As depicted in FIG. 19D, light pulses of constant intensity and lowerfrequency may be applied for generating pulses in a first mode formeasuring heart rate, in a manner similar to that depicted in FIG. 18B.Meanwhile, a second stream of light signals of various intensities maybe used to detect skin reflection characteristics. As the reflectioncharacteristics is detected and determined by the heart rate monitor, itmay adjust light intensity and/or detection gain by the heart ratemonitor, such that the optimal signal level and pattern may be measuredby the heart rate monitor.

The process for adjusting the heart rate monitor further involvesdetermining a slope of detected light value versus emitted light valuesome initial light pulses. See block 1904. In some embodiments, variousemitted light levels are provided for different slopes, which emittedlight levels provide good heart rate monitoring performance for skinconditions having comparable slopes. The process then chooses a newemitted light value based on the determined slope, correspondingpreviously provided slopes and light intensity. See block 1906. The newemitted light value is used for operating a first mode for heartbeatwaveform measurements. See block 1908.

The process further involves collecting more data points in the skincharacterization mode (see block 1910) and fitting a mathematicalrelationship to the collected more data points (see block 1912). Variousmathematical relationships may be applied depending on the data patternsbetween emitted intensity and detected intensity for different skincharacteristics. In some embodiments, the mathematical relationship islinear as shown in FIG. 19E. In other embodiments, the mathematicalrelationship is polynomial as shown in FIG. 19F. Alternativemathematical relationship may be applied in other embodiments. Theprocess further involves applying a preset detected light value known toprovide good detection reading (e.g., light intensity or power) to thefitted relationship to obtain the corresponding emitted light value. Theprocess then involves emitting light at the obtained emitted light valuecorresponding to the preset detected light value for operating the heartrate monitor in the first mode. See block 1914. In some embodiments, thecalibration process ends after the light is emitted at the obtainedvalue. See block 1916. In other embodiments, the calibration process maycontinuously and dynamically adjusts the emitted light intensity. Insome embodiments, the calibration process may adjust the gain of thephotodetector.

Some embodiments provide a method for adjusting at least one setting foroperating a heart rate monitor in a wearable fitness monitoring device.The method involves: (a) pulsing a light source in the heart monitor ina skin characterization mode by emitting a succession of light pulses,at least some having variable intensity with respect to one another; (b)detecting a variation in intensity of light from the light pulsesemitted in the skin characterization mode after the light has interactedwith the user's skin; (c) determining a response characteristic of theuser's skin from the variation in intensity of light detected in (b);and (d) using the response characteristic of the user's skin to adjust again and/or light emission intensity of the heart rate monitor operatingin a first mode for detecting one or more characteristics of the user'sheartbeat waveform.

In some embodiments, the response characteristic is dependent on anopacity value of the user's skin. In some embodiments, operating in thefirst mode and operating in the skin characterization mode are performedconcurrently. In some embodiments, operating in the first mode andoperating in the skin characterization mode concurrently involvesperiodically determining a response characteristic of the user's skinwhile continuously operating in the first mode. In some embodiments,operating in the skin characterization mode occurs no more than about50% of the time, e.g., no more than about 40% of the time, or no morethan about 30% of the time, no more than about 20% of the time, no morethan about 10% of the time, no more than about 5% of the time.

In some embodiments, operating in the first mode involves pulsing thelight source in the heart rate monitor at a first frequency anddetecting light from the light source, after the light has interactedwith the user's skin, at the first frequency. Furthermore, operating inthe skin characterization mode involves pulsing the light source in theheart rate monitor at a second frequency and detecting light from thelight source at the second frequency.

There are many concepts and embodiments described and illustratedherein. While certain embodiments, features, attributes, and advantageshave been described and illustrated herein, it should be understood thatmany others, as well as different and/or similar embodiments, features,attributes and advantages are apparent from the description andillustrations. As such, the above embodiments are merely provided by wayof example. They are not intended to be exhaustive or to limit thisdisclosure to the precise forms, techniques, materials and/orconfigurations disclosed. Many modifications and variations are possiblein light of this disclosure. It is to be understood that otherembodiments may be utilized and operational changes may be made withoutdeparting from the scope of the present disclosure. As such, the scopeof the disclosure is not limited solely to the description above becausethe descriptions of the above embodiments have been presented for thepurposes of illustration and description.

Importantly, the present disclosure is neither limited to any singleaspect nor embodiment, nor to any combinations and/or permutations ofsuch aspects and/or embodiments. Moreover, each of the aspects of thepresent disclosure, and/or embodiments thereof, may be employed alone orin combination with one or more of the other aspects and/or embodimentsthereof. For the sake of brevity, many of those permutations andcombinations will not be discussed and/or illustrated separately herein.

1-19. (canceled)
 20. A wearable monitoring device, comprising: a housinghaving a physical size and shape that is adapted to couple to a body ofa user; a periodic light source and a photo detector positioned toreceive periodic light emitted by the periodic light source; a firstlight pipe, disposed in the housing and optically coupled to theperiodic light source, to direct or transmit light from the periodiclight source along a predetermined path to an outer surface of thehousing; and processing circuitry configured to calculate a heart rateof the user using data generated by the periodic light source, whereinthe processing circuitry is configured to: (i) emit a first set of oneor more light pulses in a wavelength using the periodic light source,(ii) when the first set of one or more light pulses interacts with theuser's skin or tissue and the first set of one or more light pulses isdetected by the photo detector, initiate operation of the wearablemonitoring device in a first mode; and (ii) when the first set of one ormore light pulses is not detected by the photo detector or when thefirst set of one or more light pulses has a different intensity orpattern from a baseline intensity or pattern, initiate operation of thewearable monitoring device in a second mode, the second mode having alower power state than the first mode.
 21. The wearable monitoringdevice of claim 20, wherein the periodic light source comprises twoperiodic light sources straddling the photo detector.
 22. The wearablemonitoring device of claim 20, wherein the housing comprises a photosensor housing that protrudes at least about one (1) millimeter (mm)above a base surface of the wearable monitoring device and is configuredto press against the user's skin when worn.
 23. The wearable monitoringdevice of claim 20, wherein the processing circuitry is furtherconfigured to: determine a difference between the first set of one ormore light pulses detected by the photo detector in the first mode andthe second mode; and use the difference to determine whether thewearable monitoring device is being worn by the user or not.
 24. Thewearable monitoring device of claim 23, wherein the first mode comprisesan operational mode of the wearable monitoring device in which thewearable monitoring device continues to emit or detect light pulses andmonitor heart rate of the user.
 25. The wearable monitoring device ofclaim 24, wherein the first mode comprises emitting the first set of theone or more light pulses in a low intensity manner for a percentage oftime.
 26. The wearable monitoring device of claim 25, wherein the secondmode comprises a non-operational mode in which the wearable monitoringdevice does not emit or detect light pulses.
 27. The wearable monitoringdevice of claim 26, wherein, during the second mode, the processingcircuitry stops monitoring the heart rate of the user.
 28. The wearablemonitoring device of claim 27, wherein the processing circuitry isfurther configured to: monitor motion of the wearable monitoring device.29. The wearable monitoring device of claim 28, wherein the processingcircuitry is further configured to: switch from the second mode to thefirst mode when the motion is detected indicating that the user islikely wearing the wearable monitoring device.
 30. The wearablemonitoring device of claim 20, wherein the processing circuitry isfurther configured to: measure heart rate or other heartbeat waveformrelated signals concurrently when emitting the first set of one or morelight pulses.
 31. The wearable monitoring device of claim 20, whereinthe first set of one or more light pulses interacting with the user'sskin or tissue is detected by capturing signal variation caused byheartbeat-related blood flow in one or more capillary vessels of theuser.
 32. The wearable monitoring device of claim 20, wherein theperiodic light source comprises at least one of a PPG sensor or an LEDsensor.
 33. A wearable monitoring device, comprising: a housing having aphysical size and shape that is adapted to couple to a body of a user; aperiodic light source and a photo detector positioned to receiveperiodic light emitted by the periodic light source; a first light pipe,disposed in the housing and optically coupled to the periodic lightsource, to direct or transmit light from the periodic light source alonga predetermined path to an outer surface of the housing; and processingcircuitry configured to calculate a heart rate of the user using datagenerated by the periodic light source, wherein the processing circuitryis configured to: (i) detect motion of the wearable monitoring device;(ii) begin operating a heart rate monitor of the wearable monitoringdevice in a worn detection mode configured to detect that the wearablemonitoring device has transitioned to a worn state; (iii) within adefined time frame, enter the worn detection mode and determine whetherthe heart rate monitor detects whether the wearable monitoring devicehas transitioned to the worn state; (iv) begin operating the heart ratemonitor in a first mode configured to measure a heart rate signal of theuser; (v) periodically and temporarily operate the heart rate monitor ina second mode configured to detect an unworn state, while also operatingin the first mode; and (vi) determine whether the second mode detectsthat the wearable monitoring device has transitioned to an unworn state.34. The wearable monitoring device of claim 33, wherein the processingcircuitry is further configured to: simultaneously emit heart rate andlight pulses for probing proximity of the wearable monitoring device tothe body of the user.
 35. The wearable monitoring device of claim 34,wherein the processing circuitry is further configured to: use theemitted heart rate and light pulses for probing proximity of thewearable monitoring device to the body of the user to determine whetherthe wearable monitoring device is being worn by the user or not.
 36. Thewearable monitoring device of claim 33, wherein the processing circuitryis further configured to: operate the heart rate monitor in the firstmode while also operating in the second mode to detect near proximity ofthe wearable monitoring device to the user's skin, where the first modeis configured to determine one or more characteristics of a user'sheartbeat waveform when the wearable monitoring device is in nearproximity to the user.
 37. The wearable monitoring device of claim 36,wherein the processing circuitry is further configured to: frominformation collected in the second mode, determining that the heartrate monitor is not proximate to the user's skin.
 38. The wearablemonitoring device of claim 37, wherein the processing circuitry isfurther configured to: in response to determining that the heart ratemonitor is not proximate to the user's skin, end operating the heartrate monitor in the first mode.
 39. The wearable monitoring device ofclaim 33, wherein the processing circuitry is further configured to:operate the heart rate monitor in the second mode by pulsing theperiodic light source in the heart rate monitor at a second modefrequency and detecting light from the periodic light source at thesecond mode frequency.
 40. The wearable monitoring device of claim 33,wherein the processing circuitry is further configured to: operate theheart rate monitor in the first mode by pulsing the periodic lightsource in the heart rate monitor at a first mode frequency and detectinglight from the periodic light source at the first mode frequency. 41.The wearable monitoring device of claim 33, wherein the processingcircuitry is further configured to: operate the heart rate monitor inthe second mode by emitting a succession of light pulses of variableintensity and determining whether detected light corresponding to thesuccession of light pulses has a variable response corresponding to thevariable intensity of the emitted light pulses.